Pressure

Product information 

Pressure 

Pressure switches · Pressure transmitters 

CERTIFIED 

ISO 9001 

ISO 14001 

DVGW 

TÜV

Product Overview 

3 

Contents 

PRESSURE SWITCHES 5 

Electronic pressure switches / pressure transmitters Smart Press PST/PST-R 6 

Applications, technical data 6 

Product Summary 7 

Definitions 8/9 

Electrical connection 10 

Switch outputs, analogue output and relay output 11 

Indicators and display 12 

Settings at user level 13 

Settings at expert level 14 

Overview of adjustable parameters 15 

Dimensioned drawings 16/17 

Mechanical pressure switches 18 

Technical features (sectional drawing) 18 

Definitions 19/20 

General information about explosion protection 21/23 

Pressure monitoring in areas at risk of explosion 24 

10 selection criteria 25 

Pressure switches – General Description 26 

General technical data – valid for all pressure switches 27 

“ZF” additional functions for pressure switches and pressure monitors 28/29 

Setting instructions 30 

Pressure switch with switching state interlock (reclosing lockout) 31 

Explanation of type designations – type codes 32 

DCM pressure switches and pressure monitors for overpressure 33 

VCM vacuum switches 34 

DNM pressure switches free of non-ferrous metal 35 

DNS pressure switches with stainless steel sensor system 36 

DDCM differential pressure switches 37 

DPS differential pressure switches for ventilation and air-conditioning systems 38 

HCD pressure and differential pressure switches for neutral gases (DVGW-tested) 39 

Pressure switches with 2 microswitches – technical data, switching intervals 40/41 

Switching schemes for ZF (additional function) 217 42 

Examples of use for two-stage pressure switches 43 

Pressure switches “of special construction” 44/45 

Definitions and information 44/45 

Safety analysis for maximum pressure monitoring 46 

Further observations and summary 47 

Standards – Directives – Component tests 48 

Selection according to function and application, equipment of a boiler 49 

DA pressure monitors and limiters for maximum pressure monitoring 50 

DWR pressure monitors for steam and hot water, fuel gases and liquid fuels 51/52 

FD safety-engineered maximum pressure limiters for liquid gas installations 53 

DBS series pressure monitors and pressure limiters for particularly safety-critical applications 54 

Safety-engineered maximum pressure monitors 55 

Safety-engineered minimum pressure monitors 56 

Features of safety-engineered pressure monitors and pressure limiters 56 

Mechanical pressure switches, pressure monitors for fuel gases (DVGW–tested) 57 

Dimensioned drawings for switch housings and pressure sensors 58/59 

Accessories 60 

EX 011, EX041 series isolating amplifiers 60/61 

Pressure mediators attached to pressure switches 62 

Siphons, NPT adapters 63 

Threaded joints and valve combinations 63 

Specifications for pressure switches and isolating amplifiers 64

4 

Product Overview 

PRESSURE SWITCHES 65 

Product overview 66 

Pressure transmitters, pressure regulators, mechanical-inductive F type series 67 

Pressure transmitters with terminal connection type series F... + ED1 68 

Pressure transmitters with plug connection type series F ... + ED3 69 

Technical data 70 

Setting, operation and testing 71/72 

Dimensioned drawings 73 

Pressure transmitters; piezoresistive, 3-conductor system SN 3 74 

Pressure transmitters; piezoresistive, 2-conductor system SN 2 75 

Operator interface / operating ranges 76 

Setting and testing 77 

Dimensioned drawings 78 

DPT type series differential pressure transmitters for gaseous, non-aggressive media 79 

AZ type series plug-in digital display 80 

GT type series signal separator 81 

AP type series programmable digital display 82 

Specifications for pressure transmitters 83 

Alphabetical type index 

Type 

Page 

Type 

Page 

APT 82 

APV 82 

AZ 331 80 

DCM 33 

DDCM 37 

DGM 57 

DMW 63 

DNM 35 

DNS 36 

DPS 38 

DPT 79 

DWAM 50, 55 

DWAMV 50 

DWR 51/52 

EX 041 61 

EX 011 60 

Ex – DCM 33 

Ex – DDCM 37 

Ex – DGM 57 

Ex – DNM 35 

Ex – DNS 36 

Ex – DWR 51 

Ex – VCM 34 

Ex – VNM 34 

Ex – VNS 36 

FD 53 

FHBN ... 68/69 

FN 68/69 

FVN ... 68, 69 

GT 81 

HCD 39 

K 430 D/480 D 63 

MAU8 63 

NPT1 63 

PST 7 

PST ...-R 7 

SDBAM 50 

SN2 75 

SN3 74 

ST 12 10 

STA 12 10 

U 430 B/480 B 63 

VCM ... 34 

VCMV ... 34 

VKD 63 

VNM 34 

VNMV 34 

VNS 36 

ZF 28/29 

ZFV ... 62

Pressure switches 

5

6 


Electronic pressure switches / pressure transmitters PST, PST…-R / Smart Press 

Smart Press 

Electronic pressure switches / pressure transmitters 

PST, PST…-R 

PST, PST...R 

Applications 

Honeywell Fema PST and PST…-R series pressure 

switches are highly flexible and can be 

adjusted and configured in two modes, namely 

user mode and expert mode, and are used for 

fine adjustment and monitoring of system pressures 

in plant engineering, fluidics, process 

engineering and pneumatics, and for monitoring 

and control of pumps and compressors. 

Self-monitored versions are used in manufacturing 

lines in the automotive industry and in 

many areas of mechanical and special-purpose 

engineering. With an overall accuracy of 0.5% 

of full scale, these pressure switches/transmitters 

are also suitable for measurement monitoring 

in many laboratory applications. 

Technical data Housing and cover Polybutylene terephthalate (PBT) 

Ambient temperature -20 to + 60°C, from 36 V DC…50 °C 

Storage temperature -35 to + 80°C 

Medium temperature -20 to + 100°C 

Relative humidity 

0 to 95%, non-condensing 

Total accuracy 

0.5% of final value, 1…600 bar 

1% of final value, 250…1000 mbar 

Medium temperature drift 0.3% per 10 K 

Weight 

380 grams 

Parts in contact with medium 1.4571 + 1.4542 (high pressure) 

1.4571 + 1.4435 (low-pressure/flush) 

Process connection 

Pressure gauge connection G 1/2“ external thread 

Flush connection 

G 3/4” external thread 

Electrical connection PST versions 5-prong M12 plug, A-coded as per 

DIN IEC 60947-5-2 

PST…-R version 

Extra 3-prong M12 plug 

Protection class II as per EN 60335-1 

Degree of protection IP65 according to EN 60529 

Climate class C as per DIN EN 60654 

Power supply 

14…36 V DC, max. 100 mA 

EMC 

compatible as per EN61326/A1 

Electronic Outputs 2, configurable as high/low side or 

switch outputs 

push-pull switches, 14…36 V DC, 

(all versions) 

max. 250 mA 

Reaction time 

30 ms 

Switching differential (SP/RP) selectable via software 

Minimum Switching differential = ^ resolution of the display 

Relay outputs Contact type 1 switch-over contact (1 x UM) 

(PST..-R series) Min. electrical lifetime 250,000 switching cycles 

Switching capacity AC1 (resistive load) 1.5VA (24 VDC/60 mA, 230 VAC/6.5 

mA) 

Gold contacts AC15 (inductive load) unsuitable 

(AgSnO2+Au [5 μm]) Max. switching capacity 60 mA for < 5 ms 

Min. switching capacity 

50 mW (>5 V or >2 mA) 

Switching capacity AC1 (resistive load) 690 VA (230 V AC / 3 A) 

Silver contacts AC15 (inductive load) 230 VA (230 V AC / 1 A) 

(AgSnO2) Max. switching capacity 30 A for < 5 ms 

Min. switching capacity 

500 mW (>12 V or >10 mA) 

Diagnostic output Output configuration “WARN” output (plug 2) max. 20 mA, 

14…36 V DC 

Transmitter output Voltage/current 0…10 V and 4…20 mA, configurable 

(analogue output) 

in expert mode 

Range limitation 

Measuring range can be limited by up 

to 50% FS 

Step response 

approx. 300 ms 

Simulation mode System pressure simulation via pressure range 

Reaction test on sensor 

signals 

4 x/sec…1 x/16 sec



7 

Product Summary 

PST = Pressure Switch + 

Transmitter 

PST…R = Pressure Switch + 

Transmitter + Relay 

01 = –1…+1 bar 

002 = 0–1.6 bar 

004 = 0–4 bar 

010 = 0–10 bar 

025 = 0–25 bar 

060 = 0–60 bar 

100 = 0–100 bar 

250 = 0–250 bar 

600 = 0–600 bar 

250 = 0–250 mbar 

400 = 0–400 mbar 

600 = 0–600 mbar 

001 = 0–1000 mbar 

G12S 

G34F 

= G 1/2‘‘ Standard pressure 

gauge version 

= G 3/4” quasi-flush version 

PST V 01 R G34F -R 

V 

M 

= Vacuum version 

= Millibar version 

R 

A 

= Relative pressure sensor 

= Absolute pressure sensor 

R 

= Relay output of electrically isolated 

changeover contact 

Ordering data 

Smart Press with 2 electronic switching 

channels + transmitteroutput 

Order no. 

Pressure in bar 

PSTM250RG12S 0…250 mbar 



PSTV01RG12S 

–1…+1 

PST001RG12S 0…1 

PST002RG12S 

0…1.6 

PST004RG12S 0…4 

PST010RG12S 0…10 

PST025RG12S 0…25 

PST060RG12S 0…60 

PST100RG12S 0…100 

PST250RG12S 0…250 

PST600RG12S 0…600 

PSTM250RG34F 0…250 mbar 



PSTV01RG34F 

–1…+1 

PST001RG34F 0…1 

PST002RG34F 

0…1.6 

PST004RG34F 0…4 

PST010RG34F 0…10 

PST025RG34F 0…25 

Smart Press with 2 electronic switching 

channels + transmitteroutput 

and relay output 

Order no. 

Pressure in bar 

PSTM250RG12S-R 0…250 mbar 



PSTV01RG12S-R –1…+1 

PST001RG12S-R 0…1 

PST002RG12S-R 0…1.6 

PST004RG12S-R 0…4 

PST010RG12S-R 0…10 

PST025RG12S-R 0…25 

PST060RG12S-R 0…60 

PST100RG12S-R 0…100 

PST250RG12S-R 0…250 

PST600RG12S-R 0…600 

PSTM250RG34F-R 0…250 mbar 



PSTV01RG34F-R –1…+1 

PST001RG34F-R 0…1 

PST002RG34F-R 0…1.6 

PST004RG34F-R 0…4 

PST010RG34F-R 0…10 

PST025RG34F-R 0…25 

Max. Bursting Dimensioned 

permissible pressure drawing 

pressure in bar Page Fig. 

in bar 

1 > = 1.6 

2 > = 3.2 

2 > = 3.2 

6 > = 10 

6 > = 10 

6 > = 10 16 30+31 

12 > = 20 

30 > = 50 

75 > = 125 

180 > = 300 

300 > = 500 

500 > = 1600 

1000 > = 1800 

16 32+33 

1 > = 1.6 

2 > = 3.2 

2 > = 3.2 

6 > = 10 

6 > = 10 17 34+35 

6 > = 10 

12 > = 20 

30 > = 50 

75 > = 125 

PST002AG12S 0…2 

PST010AG12S 0…10 

PST002AG12S-R 0…2 

PST010AG12S-R 0…10 

6 > = 10 

30 > = 50 

16 30+31 

PST002AG34F 0…2 

PST010AG34F 0…10 

PST002AG34F-R 0…2 

PST010AG34F-R 0…10 

6 > = 10 

30 > = 50 

17 32+33

8 



Definitions 

e.g. 3.5 bar 

Maximum pressure monitoring 



If an output is configured as a maximum detector, the electronic pressure switch monitors a programmed 

upper pressure limit. A switching process is triggered as soon as the pressure exceeds 

this limit. 

e.g. 3.0 bar 

= active 

= inactive 

Time 

Minimum pressure monitoring 

If an output is configured as a minimum detector, the electronic pressure switch monitors a programmed 

lower pressure limit. A switching process is triggered as soon as the pressure falls below 

this limit. 



e.g. 1.0 bar 

e.g. 0.5 bar 

= active 

Window monitoring 

If an output is configured for pressure window monitoring, the electronic pressure switch monitors a 

programmed pressure window, i.e. the range between a defined lower limit and a defined 

upper limit. A switching process is triggered as soon as the pressure falls below the lower pressure 

limit or exceeds the upper pressure limit. 

Electronic pressure switch 

PST and PST…-R series electronic pressure switches consist of an electronic, piezoresistive pressure 

sensor and a downstream analyser with 2 independently programmable switching channels, an 

analogue output and an optionally configurable relay output. 

= inactive 

Window monitoring 

Time 

Switching differential 

In contrast to mechanical pressure switches, where the switching differential is essentially determined 

by the design, with electronic pressure switches any switching differential may be chosen. The difference 

between the switching point and the reset point (the switching differential) is defined at user level 

by entering and saving the switching and reset points via the software. The smallest definable switching 

differential corresponds to the display resolution. 

Switching point and reset point 

Any switching point (SP) and reset point (RP) across the entire nominal pressure range of the electronic 

pressure switch can be selected at user level via the software. 

Switching point deviation 

Illegal settings are automatically detected by the software. The value most recently set has priority over 

the value first set. If the electronic pressure switch is configured as a maximum detector, for example, 

the switching point (SP) must lie above the reset point (RP). If the reset point is above the 

switching point, or the switching point is below the reset point, no error will be displayed, but the 

switching points will be shifted accordingly until they are finally saved. 

Time Out function 

“Time Out” refers to the time window in which values can be entered without the display automatically 

reverting to pressure display mode. For all settings at user level the setting window is 1 minute. 

This means that if the user does not enter anything for one minute during the setting process, the unit 

automatically reverts to display mode and shows the current pressure in the display, disregarding any 

values that have been entered but not saved. However, when the unit is in setting mode at expert 

level, this “Time Out” function is turned off. In other words, the display (and thus the unit) remain in 

setting mode until the settings are saved in expert mode.



9 

Escape function 

After entering a valid 4-digit code, the user is able to parameterise and configure the unit at user or 

expert level. However, the unit automatically reverts to the locked state if no adjustment activity takes 

place within 60 seconds. Any manipulation of the rotary/push button extends the setting time by a further 

60 seconds. On returning to the locked state, the word “CODE” (instead of “EXP”) appears in the 

corresponding screen. Once the correct code has been entered, the settings can be changed both in 

user mode and in expert mode. 

In expert mode it is also possible to change the code. While the unit is in expert mode, if values or 

settings are changed but not saved (with “SAVE”), the unit will remain in expert mode until a defined 

state is chosen with “SAVE” or “REST” (restore data). If the code is set to “0000” in expert mode and 

this state is saved (with “SAVE”), the unit remains in the unlocked condition. In this case the “Escape” 

function is disabled. 

Simulation 

To check the connection configuration or the reaction of the system to output signals, the “SIM” setting 

can be used to simulate the pressure for which the unit is designed. The pressure can be varied 

from 0-100% of the total value with a rotary switch. 

To show the reaction limits of the system it is also possible to set an alternating output signal with a 

variable pulse frequency (0 - 100% = 4x/sec …1x/16 sec). If simulation mode is not used for 30 minutes, 

the unit automatically reverts to display mode. 

Electronic slave pointer 

Smart Press allows you to trace a failure event back in time. The hours are counted, starting from the 

failure event until the readout date. This enables the system operator to determine when the failure 

occurred and so draw conclusions about any plant errors. 

Zero adjustment 

Zero adjustment is used to compensate any drift error of the sensor, which is liable to occur on all 

sensors during the lifecycle of the product. With zero adjustment, SmartPress allows you to set the 

display precisely to zero at zero pressure. The position of the adjustment curve is simply moved in parallel. 

The basic adjustment of the sensor is not changed. Zero adjustment is only possible within a 

range of +/– 2% of the overall pressure range. Therefore a position error, which is particularly liable to 

occur on sensors in the range of 0-1 bar, can easily be compensated. As the setting range is very 

small, it is virtually impossible for the sensor to be accidentally zeroed on pressurization. 

Push/pull output 

In expert mode the switch outputs can be configured as traditional open collector or push/pull outputs. 

The outputs always assume defined states (e.g.: unswitched: minus potential, switched: plus 

potential). If the outputs are applied to the input of a PLC, any pull-down resistors 

that would otherwise be necessary can be dispensed with. 

Adjustment dynamics 

The bit generator of the SmartPress has been redesigned. The time-consuming job of “scanning” with 

the adjusting knob has given way to a convenient, dynamic setting strategy. 

This allows the user to find the desired setting with just a few turns of the handwheel.

10 



Electrical connection 

Electrical connection and contact assignment 

Electrical connection is via M12 plugs on the back of the unit. Depending on the version, either 

2 (PST) or 3 (PST…-R) M12 connector plugs are available (not supplied with the unit). 

Contact assignment on plug 1 

Pin 1: Supply voltage 14…36 VDC 

Pin 2: OUT 2 (output 2) open collector output 

Pin 3: 0 volt (ground) 

Pin 4: OUT 1 (output 1) open collector output 

Pin 5: Serial interface (locked for calibration) 

Special characteristic of open collector outputs: 

Depending on the design, the output voltage at open collector outputs can be up to 2.5 V lower than 

the applied supply voltage. 

Example: Supply voltage 14 V… output voltage OUT 1 approx. 11.5 V. 


All versions of series PST and PST…-R are also equipped with an A-coded M 12 plug. 

Pin 1: Supply voltage 14…36 VDC 

Pin 2: WARN (warning output max. 20 mA) 

Pin 3: 0 V (ground) 

Pin 4: Analogue output AOUT 

Pin 5: Serial interface (for factory calibration only) 

Units of the PST series can be powered both via plug 1 and via plug 2. If the PST is used purely as a 

transmitter, only one connection via plug 2 is needed, because the supply voltage can be connected 

here too (see “Contact assignment on plug 1”). 


All versions of series PST…R are also equipped with a B-coded M 12 plug. 

Suitable cable sockets should be ordered at the same time for the electrical connection. 

Optional accessories 

Cable socket 

5-pole ST12-5-G straight version 

5-pole ST12-5-A right-angle version 

4-pole ST12-4-G straight version with 2 m cable 

4-pole ST12-4-A right-angle version with 2 m cable 

Plug protection cap 

IP67 STA12 

NB – For IP65 special plug protection cap STA12 is required 

Observance of IP65 water and dust proofing requires the secure sealing of electrical connections not 

closed with plugs. 

The soft rubber dust caps fitted for shipping do not fulfil this requirement. A reliable seal can only be 

achieved by the STA12 protection cap.



11 

Switch outputs 

Switch output OUT1 and OUT2: 

The switch outputs can be configured via the software (at expert level) both as normally closed / normally 

open, and as high-side and low-side switching. 

low-side switching 

high-side switching 

· In normally closed configuration, the selected voltage potential (ground or supply voltage) occurs 

at the output in the unswitched state. 

· In normally open configuration, the selected voltage potential (ground or supply voltage) occurs at 

the output in the switched state. 

· In the low-side switching configuration, the outputs switch the voltage potential 0V (ground) with 

respect to a consumer connected to OUT1 or OUT2. 

· In the high-side switching configuration, the outputs switch the supply voltage potential (minus 

approx. 2V) with respect to a consumer connected to OUT1 or OUT2. 

If the power supplies of the pressure switch and connected load are independent of one 

another, the following must be taken into account: The potential difference between OC output 

and ground and OC output and supply voltage must not exceed 36 VDC. If the unit is 

configured for low-side switching, the external supply voltage must have the same ground 

reference as the unit itself. If the unit is defined as high-side switching, the external supply 

voltage must be linked to the supply voltage of the unit. It is important to note that the voltage 

drop in the through-connected state can be as much as 2 V. The maximum permitted 

current at the OC is 250 mA per switch output (OUT1, OUT2). A maximum switching current 

of 250 mA may flow through each channel. 

The switching channels are short-circuit-proof and they are monitored for current and temperature. 

Where current limiting is used and on overheating, both LEDs light up red (WARN function). 

The freely configurable outputs can connect both the supply voltage (+ potential) itself and the ground 

(– potential) of the supply voltage to the output. If plus potential exists at the output, ground minus 

potential occurs after switching over. 

If ground minus potential exists at the output, plus potential occurs after switching over. 

High-side switching push/pull outputs 

Advantage: The output behaves like a mechanical changeover contact which emits either plus or 

minus potential. In other words, the open output is never electrically undefined, as is the case with an 

open collector output. Pull-up resistors are therefore unnecessary. 

Analogue output and relay output 

plug 3 

Analogue output AOUT: 

The analogue output (AOUT) is available in versions PST and PST…-R. In expert mode it is configurable 

both as a 0-10 V/10-0 V, and as a 4–20 mA/20–4 mA output. The unit is supplied with the output 

configured for 0-10 V. The input impedance of the connected consumer must not exceed 500 

ohms. 

Relay output REL: 

The relay output is available in version PST…-R. In expert mode the analogue output can be coupled 

via the software with output 1 (OUT1) and output 2 (OUT2), and with the WARN function. This means 

that the user can choose a potential-free output for these 3 important functions. The changeover contact 

of the relay is designed for a maximum resistive load of 4 A and an inductive load of 200 VA. At 

the lower end the 5 μ gold-plated silver contacts are designed for a minimum load of 50 mW. (5 V at 

10 mA). 

It should always be remembered that after a one-off maximum load, use at minimum load is 

no longer possible.

12 



Indicators and display 

The indicators in the display 

have the following meanings: 

ATT 

EXPERT 

WARN 

WIN 

Attenuation (for setting a filter) 

Expert mode (allows the user to 

configure the unit, e.g. as maximum 

detector or minimum detector 

or for window monitoring) 

Warning function / alarm 

Window monitoring (for monitoring 

a pressure window to detect 

exceeding or falling below a 

selected pressure window) 

OUT1 Switch output OC 1 

OUT2 Switch output OC 2 

SP 

RP 

AOUT 

ZERO 

FSO 

INV 

Switching point 

Reset point 

Switch contact configured as normally 

open 

Switch contact configured as normally 

closed 

Analogue output (if the current 

pressure is outside the currently 

set range, the “AOUT” symbol is 

not visible). 

Zero point display for the analogue 

output or display symbol if output 

1 or output 2 defined as low-side 

switching (unit switches power 

supply plus to the output). 

Combined with “FSO” in the 

switch configuration menu as indicator 

for the push/pull function. 

Upper limit of the selected analogue 

display range or display 

symbol if output 1 or 2 defined as 

high-side switching. (unit switches 

power supply minus to the output). 

Combined with “ZERO” in the 

switch configuration menu as indicator 

for the push/pull function. 

Inversion of the analogue signal 

(i.e. “INV” appears if, instead of a 

standard analogue signal 0…10 V 

or 4…20 mA, the analogue signal 

output is set to 10…0 V or 

20…4 mA). 

Display 

The unit has a 4-place digital display with 3 decimal points and a minus sign. There are also other 

symbols for the different settings and configurations. 

The display also includes a bar graph. This is at the top of the display and consists of a row of separately 

addressable individual segments with arrow symbols at either end. 

As soon as the unit is powered up, all symbols appear on the display for 1 second as a test and the 

two LEDs light up briefly. The unit then goes into display mode, showing the current system pressure 

and the selected unit (bar, PSI or Pa). In addition the pressure trend (falling or rising) is indicated by an 

arrow at the left (falling) or right (rising) end. The “AOUT” indicator tells the user that the pressure is 

currently in the predefined pressure range for the analogue signal. 

Meaning of LED colours 

LED status 

Meaning 

LED 1 LED 2 Output 1 Output 2 

lit lit Status Status 

green green inactive inactive 

green orange inactive active 

orange green active inactive 

orange orange active active 

red red SP/RP implausible 

red red error 

Status LEDs 

The current status of the switch outputs is displayed by 2 LEDs located beneath the display (LED 1 and 

LED 2). The two 3-colour LEDs indicate the switching status of the corresponding output and the 

warning function. 

· Orange: the output is ACTIVE 

· Green: the output is INACTIVE (if defined as WARN output, likewise INACTIVE) 

· During input of the switching points, only the LED of the switching channel currently being modified 

is active. When switching points are entered, if an implausible entry is made for the maximum detector, 

e. g. SP < RP, the relevant channel LED lights up red. 

· Both status LEDs light up red as soon as a WARN state occurs (e. g. electronics faulty and unit overheating). 

Warning with both LEDs RED and WARN output active 

Display indication 

- on sensor failure -***1 

- under-voltage -**1* 

- under-temperature -*1** 

- over-temperature -*2** 

Display indication 

- overload output 1 -1*** 

- overload output 2 -2*** 

- overload output 1 and 2 -3***



13 

Settings at user level 

Switch output OUT 1 and OUT 2 

At user level, the switching point (SP) and reset point (RP) can be set across the entire nominal pressure 

range. 

When the DIG (digital incremental sensor) is turned by one notch in the clockwise direction, the symbol 

“OUT 1” and “SP” appears. When the DIG is pressed, the EDIT “symbol” appears. 

After that, any switching point can be selected by turning the DIG clockwise or anticlockwise. When 

you press the DIG again, “SAVE” is displayed. Press the DIG again to confirm. The chosen switching 

point is now permanently saved. 

Turn it clockwise again to display the reset point (RP) symbol. The reset point (RP) is set in the same 

way as the switching point (SP). 

Analogue output (AOUT) 

Turning the DIG clockwise again opens the analogue output (AOUT) window. The screen displays the 

lower pressure value set (AOUT ZERO). Press the DIG to enter “EDIT” mode and then “SAVE” to save 

the lower reference value permanently. 

Turn the DIG again to set “AOUT” “FSO”. Here you can alter the upper reference value. The pressure 

value can be changed in the way described above. 


without filter 

setting 

with filter 

setting 

Time 

Filter setting (attenuation) 

To make the pressure switch insensitive to pressure peaks and to avoid distorting the measured value 

due to pressure peaks, a filter value of 0…95% can be set. After setting the switching points of 

OUT 2, turn the DIG again to open the “ATT” window. After pressing the DIG the user can change the 

value in edit mode (EDIT) or turn the filter off completely (OFF). Save the selected filter value with 

“SAVE”. It is now permanently stored in the memory. The currently measured pressure is compared 

with the pressure measured previously. The currently measured pressure is then attenuated depending 

on the selected degree of filtering. This attenuation affects all outputs, i. e. all open collector outputs 

and relay outputs as well as the analogue output, as the attenuation has a direct influence on the 

incoming sensor signal. The previously measured pressure and the currently measured pressure (internally 

offset against each other) always produce a weight of 100%. The filter attenuation (effect) can be 

mathematically expressed as follows: 

R[x] = M[x] * (100% - F) + R[x - 1] * F 

where: 

“F” is the selected attenuation in %, 

“M[x]” is the measured value as a function of a defined time “x”, 

“R[x - 1]” is the previously displayed and output (calculated) measured value “x - 1”, and 

“R[x]” is the displayed and output (calculated) measured value in the time “x”. 

Electronic slave pointer 

Before you exit user mode, the Smart Press shows the extreme states in the past by means of 

right/left bar graph arrows and maximum values in the vacuum/overpressure range. Press DIG 

once to enter “EDIT” mode and turn the knob to see how much time has passed since the event 

occurred.

14 



Settings at expert level 

Configuration of OUT 1 and OUT 2 

The last menu item in user mode (EXP) allows you to enter expert mode (after entering a code if necessary). 

The screen shows the configuration of OUT 1 (e.g. as WIN monitor for pressure window monitoring). 

Press the DIG to enter edit mode (EDIT). Output 1 can be configured as a minimum detector 

(left arrow), maximum detector (right arrow) or for pressure window monitoring (WIN) and as a 

push/pull output. Press to confirm your selection and open the function screen (FCT 1) of output 1. 

Press to enter edit mode (EDIT) and configure output 1 as normally open (NO), normally closed (NC), 

high-side or low-side switching or as a push/pull output. 

OUT 2 is configured in the same sequence, but note than output 2 can also be configured as a 

WARN output. 

Configuration of analogue output (AOUT) 

Turn the DIG clockwise again to open the configuration menu (AOUT). The screen shows either FCTA 

(current output) or FCTV (voltage output). In EDIT mode the analogue output can be configured as 

current or voltage output, or inverted. 

Allocation of relay contact (on PST…-R versions only) 

Turn the DIG clockwise again to enter the relay output configuration mode (REL). Press to switch to 

EDIT mode. Turn to apply the relay function to OUT 1, OUT 2 or WARN. The OC outputs are not 

affected by this. That is to say, the relay function should always be regarded as parallel to the corresponding 

output. 

Setting pressure units to bar, Pascal or PSI 

Turn the DIG clockwise again to enter the “UNIT” menu. Press and turn to select and confirm the 

desired pressure unit. 

Setting the display background lighting 

Select the menu option LED+ at expert level and “EDIT”, then choose LED+ (permanently lit) or 

LED– (switching off automatically). 

Simulation mode 

Smart Press allows you to simulate various system states for checking connections and functions. 

Select menu option SIM1 to take the system pressure through 0-100% according to the sensor specification. 

Selected switching points and the analogue output can be checked during this process. 

The menu option SIM2 allows you to initiate an alternating square wave signal with a variable pulse frequency. 

In this way you can test the system’s ability to react to sensor signals. If the display shows 

SIM--, simulation mode is turned off. 

Setting a four-digit locking code 

Turn the DIG clockwise again to enter the “CODE” menu. Press to enter EDIT mode, where you can 

enter and confirm a four-digit code between 0001 and 9999. 0000 is not a code. 

Exiting expert level via the EXIT menu 

Turn the DIG clockwise again to enter the “EXIT” menu. Press to go directly to display mode or to the 

SAVE menu (if any value has been modified). Here you can either confirm the new state with SAVE, or 

go back to the previous state (which existed before the modification) with REST (Restore).



15 

Overview of adjustable parameters 

Activity / Situation Indications in LCD display Parameters modifiable in 

Symbols Digital values/text User mode Expert mode 

Current pressure is displayed* 

Current pressure , relevant unit relevant digital value – – 

Output OUT 1 active OUT 1 – – – 

Output OUT 2 active OUT 2 – – – 

AOUT (pressure between ZERO and FSO) AOUT – – – 

Rising pressure – – – 

Falling pressure – – – 

Alarm (sensor, power supply etc.) WARN ***1, **1* etc. No No 

Parameterisation of outputs OUT 1 (and OUT 2)* 

SP , OUT1 (OUT2), SP digital value Yes No 

RP , OUT1 (OUT2), RP digital value Yes No 

1. Window (WIN) setting , OUT1 (OUT2), SP digital value Yes No 

2. Window (WIN) setting , OUT1 (OUT2), RP digital value Yes No 

Configuration of outputs OUT 1 (and OUT 2) 

Maximum pressure monitor (SP>RP) EXPERT, SP, RP, OUT1 (OUT2) No Yes 

Minimum pressure monitor (SP

16 



Dimensioned drawings 

30 31 

32 33



17 

34 35

18 


Mechanical pressure switches 


Technical features / Advantages 

Diecast aluminium housing 

IP 54 or IP 65 

version also available 

Wall mounting 

or directly on the pressure line 

Switching element (microswitch) 

Lead sealable setpoint adjustment 

Setting spindle locking element 

Terminal connection 

or plug connection to 

DIN 43 650 Form A 

Stainless steel sensor housing 

Stainless steel bellows 

with internal stop 

Pressure connection 

G 1/2“ external 

G 1/4” internal 

Centring pin



19 

Definitions 

Pressure data 

Overpressure 

Vacuum 

Absolute pressure 

Pressure over atmospheric pressure. The reference point is atmospheric pressure. 

Pressure under atmospheric pressure. The reference point is atmospheric 

pressure. 

Pressure relative to absolute vacuum. 

Differential pressure Difference in pressure between 2 pressure measuring points. 

Relative pressure 

Overpressure or vacuum relative to atmospheric pressure. 

Pressure data in all FEMA documents refer to relative pressure. 

That is to say, they concern pressure differentials relative to atmospheric pressure. Overpressures have 

a positive sign, vacuums a negative sign. 

Permissible bursting pressure (maximum permissible pressure) 

The maximum working pressure is defined as the upper limit at which the operation, switching reliability 

and water tightness are in no way impaired (for values see Product Summary). 

Bursting pressure (test pressure) 

Type-tested products undergo a pressure test certified by TÜV affirming that the bursting pressure 

reaches at least the values mentioned in the Product Summary. During the pressure tests the measuring 

bellows are permanently deformed, but the pressurized parts do not leak or burst. The bursting pressure 

is usually a multiple of the permissible working pressure. 

Setting range 

Pressure range in which the cutoff pressure can be set with the setting spindle. 

Pressure units 

Unit bar mbar Pa kPa MPa (psi) Ib/m 2 

1 bar 1 1000 10 5 100 0.1 14,5 

1 mbar 0.001 1 100 0.1 10 -4 0.0145 

1 Pa 10 -5 0.01 1 0.001 10 -6 1.45 · 10 -4 

1 kPa 0.01 10 1000 1 0.001 0.145 

1 MPa 10 10 4 10 6 1000 1 145 

1 psi 0.069 68.94 6894 6.894 0.00689 1 

In FEMA documents pressures are stated in bar or mbar. 

Pressure data for a pressure 

switch based on the example of 

DWR 625: 

Setting range: 0.5–6 bar 

Perm. working pressure: 20 bar 

Bursting pressure: >100 bar 

Important: 

All pressure data are overpressures or vacuums relative to atmospheric pressure. 

Overpressures have a positive sign, vacuums a negative sign.

20 



Definitions 


RSP =SP –xd 


RSP =SP+xd 


The switching differential (hysteresis) is the difference in pressure between the switching point (SP) 

and the reset point (RSP) of a pressure switch. Switching differential tolerances occur due to tolerances 

in the microswitches, springs and pressure bellows. Therefore the data in the Product 

Summaries are always average values. In the case of limiter functions the switching differential has no 

significance, as one is only interested in the switching point at which cutoff occurs, not the reset point. 

For a controller function, i.e. in the case of pressure switches used to switch a burner, pump etc. 

on and off, a pressure switch with an adjustable switching differential should be chosen. 

The switching frequency of the burner or pump can be varied by changing the switching differential. 

Adjustable switching differential / Calibration 

In the case of pressure switches with adjustable switching differential, the hysteresis can be set within 

the specified limits. The switching point (SP) and reset point (RSP) are precisely definable. When setting 

the pressure switch, the switching differential situation and the type of factory calibration must be 

taken into account. Some pressure switches (e.g. minimum pressure monitors of the DCM series) are 

calibrated under “falling” pressure, i.e. switching under falling pressure takes place at the scale value 

with the switching differential lying above it. The device switches back at scale value + switching differential. 

If the pressure switch is calibrated under rising pressure, switching takes place at the scale 

value and the device switches back at scale value — switching differential (see direction of action). 

The calibration method is indicated in the data sheets. 

Direction of action 

In principle, any pressure switch can be used for both maximum pressure and minimum pressure 

monitoring. This excludes pressure limiters, whose direction of action (maximum or minimum) is predefined. 

The only thing to remember is that the scale reading may deviate by the amount of the switching 

differential. See example at bottom left: The scale value is 2.8 bar. 


With rising pressure, switching takes place once the preset switching pressure is reached (SP). The 

reset point (RP) is lower by the amount of the switching differential. 


With falling pressure, switching takes place once the preset switching pressure is reached (SP). 

The reset point (RP) is higher by the amount of the switching differential. 

Direction of action in vacuum range 

It is particularly important to define the direction of action in the vacuum range. 

Rising does not mean a rising vacuum, but rising pressure (from the point of view of absolute “0”). 

“Falling” pressure means a rising vacuum. 

Example: Vacuum switch set to –0.6 bar falling means: Switching (SP) takes place under falling pressure 

(rising vacuum) at –0.6 bar. The reset point is higher by the amount of the switching differential 

(e.g. at –0.55 bar). 

Setting a pressure switch 

To define the switching point of a pressure switch exactly, in addition to the pressure it is also necessary 

to determine the direction of action. “Rising” means that switching takes place at the set value 

when the pressure rises. 

The reset point is then lower by the amount of the switching differential. “Falling” means exactly the 

opposite. 

Please note when specifying the setting of a pressure switch: 

In addition to the switching point it is also necessary to specify the direction of action (falling or rising). 

Example for selection of a pressure switch: 

A pump is to be turned on at 2.8 bar and off again at 4.2 bar. 

Chosen type: DCM6-203 according to data sheet DCM. Setting: Scale pointer to 2.8 bar (lower 

switching point). Switching differential to 1.4 bar (set according to pressure gauge). 

Cutoff point: 2.8 bar +1.4 bar = 4.2 bar.



21 

General information about 

explosion protection 

Basic principle 

The basic principle of explosion protection is that: 

a) combustible materials (gas, vapour, mist or dust) in dangerous quantities 

b) air (or oxygen) 

c) ignition sources 

must not occur in the same place. 

The permanent or temporary occurrence of explosive mixtures as per a) and b) is often unavoidable, 

therefore when operating electrical installations care must be taken to ensure that no ignition sources 

can occur. 

With this in mind, the CENELEC technical committee has adopted the following European standards 

which are recognized in all EU member states. 

· General requirements EN 50 014 · Pressure resistant encapsulation “d” EN 50 018 

· Oil encapsulation “o” EN 50 015 · Increased safety “e” EN 50 019 

· Overpressure encapsulation “p” EN 50 016 · Intrinsic safety “i” EN 50 020 

· Sand encapsulation “q” EN 50 017 · Cast encapsulation “m” EN 50 028 

The guidelines relevant to FEMA products – besides the “General Requirements EN 50 014” – are 

“Pressure resistant encapsulation d” and “Intrinsic safety i”. 

In addition, all explosion protection guidelines issued up to the present time have been combined into 

a single European Ex-Protection Directive 94/9EC. The aim of this new harmonized directive is to bring 

the explosion protection regulations of European member states into line with one another and eliminate 

barriers to trade between partner states. The new Directive 94/9EC (ATEX 100a), which came 

into force on 1 July 2003, replaces all previous directives. 

All FEMA ex-pressure switches and ex-thermostats meet the requirements of the new European Ex- 

Protection Directive 94/9EC (ATEX 100a). 

EEx-d 

Pressure resistant encapsulation “d” 

Switching elements and other electrical function units capable of igniting an explosive mixture are cast 

in a housing capable of withstanding the explosive pressure caused by an explosion indoors and preventing 

transmission to the surrounding atmosphere. 

EEx-i 

Intrinsic safety “i” 

The equipment used in the area at risk of explosion contains only intrinsically safe electric circuits. An 

electric circuit is only intrinsically safe if the quantity of energy is so small that no spark or thermal 

effect can occur. 

The term “simple electrical equipment” 

In view of the use of simple microswitches without additional capacitance or inductance generating 

components, our pressure switches and thermostats designed for protection type Ex-i fall in the category 

of “simple electrical equipment”. These are not subject to testing or certification requirements 

within the meaning of Directive 94/9EC. The units may only be used in conjunction with ATEX-tested 

isolating amplifiers in areas at risk of explosion. We equip all units which are explicitly designed for 

such use with microswitches having gold contacts, a grounding screw and — for ease of identification 

— a blue cable entry.

22 





Zone classification 

Explosion risk areas are grouped into zones according to the likelihood of a dangerous explosive 

atmosphere according to EN 1127-1 occurring. 

When assessing the explosion hazard, i.e. when identifying explosion risk areas, the “Guidelines for 

the Avoidance of Danger due to Explosive Atmospheres with Examples (ExRL)” of the German 

Insurance Association for the Chemical Industry [Berufsgenossenschaft Chemie] must be taken into 

account. 

If the situation concerns a special case or if doubts exist as to the definition of explosion risk areas, the 

matter shall be decided by the supervisory authorities (Trade Supervisory Office [Gewerbeaufsichtsamt], 

where applicable with the assistance of the Insurance Association or the Technical Control 

Boards [Technische Überwachungsvereine]). 

In Zones 0 (20) and 1 (21), only electrical equipment for which a type test certificate has been issued 

by a recognized testing agency may be used. In Zone 0 (20), however, only equipment expressly 

authorized for that zone may be used. Equipment approved for use in Zones 0 (20) and 1 (21) may 

also be used in Zone 2 (22). Under the new European Directive 94/9 EC (ATEX 100a), a distinction is 

made between gas atmospheres and dust atmospheres. This results in the following zone classifications: 

Gas 

Dust 

Zone 0 

Zone 0 (gas) is a place in which a dangerous explosive 

atmosphere is present continuously or for long periods. This 

normally includes only the interior of containers or the interior 

of apparatus (evaporators, reaction vessels etc.), if the conditions 

of Zone 0 are fulfilled. Continuous danger > 1000 

hours/year. 

Zone 1 occasionally Zone 1 (gas) is a place in which a dangerous explosive 

atmosphere can be expected to occur occasionally in normal 

operation. This may include the immediate vicinity of Zone 0. 

Occasional danger = 10 to 1000 hours/year. 

Zone 2 

Zone 20 

continuously or 

for long periods 

seldom and for 

short periods 

continuously or 

for long periods 

Zone 2 (gas) is a place in which a dangerous explosive 

atmosphere can be expected to occur only rarely and then 

only for short periods. This may include areas surrounding 

Zones 0 and/or 1. Danger only under abnormal operating conditions 

< 10 hours/year. 

Zone 20 (dust) is a place in which a dangerous explosive 

atmosphere in the form of a cloud of dust in air is present 

continuously or for long periods, and in which dust deposits of 

unknown or excessive thickness may be formed. Dust 

deposits on their own do not form a Zone 20. Continuous 

danger > 1000 hours/year. 

Zone 21 occasionally Zone 21 (dust) is a place in which a dangerous explosive 

atmosphere in the form of a cloud of dust in air may occasionally 

occur in normal operation, and in which deposits or layers 

of inflammable dust may generally be present. This may also 

include the immediate vicinity of Zone 20. Occasional danger 

= 10 to 1000 hours/year. 

Zone 22 

seldom and for 

short periods 

Zone 22 (dust ) is a place in which a dangerous explosive 

atmosphere may be expected to occur only rarely and then 

only for short periods. This may include areas in the vicinity of 

Zones 20 and 21. Danger only under abnormal operating conditions 

< 10 hours/year.



23 



Explosion group 

The requirements for explosion-protected equipment depend on the gases and/or vapours present on 

the equipment and on the dusts lying on, adhering to and/or surrounding the equipment. This affects 

the gap dimensions required for pressure-proof encapsulation and, in the case of intrinsically safe circuits, 

the maximum permitted current and voltage values. Gases, vapours and dusts are therefore 

subdivided into various explosion groups. 

The danger of the gases rises from explosion group IIA to IIC. The requirements for electrical equipment 

in these explosion groups increase accordingly. Electrical equipment approved for IIC may also 

be used for all other explosion groups. 

Temperature class 

The maximum surface temperature of an item of equipment must always be lower than the ignition 

temperature of the gas, vapour or dust mixture. The temperature class is therefore a measure of the 

maximum surface temperature of an item of equipment. 

Temperature class Ignition temperature °C Maximum surface temperature 

°C 

T1 > 450 450 

T2 > 300 300 

T3 > 200 200 

T4 > 135 135 

T5 > 100 100 

T6 > 85 85 

Identification of explosion-protected electrical equipment 

In addition to normal data (manufacturer, type, serial number, electrical data), data relating to the explosion 

protection must be included in the identification. 

Under the new Directive 94/9EC (ATEX 95), based on IEC recommendations, the following identification 

is required: 

For example: II G D EEx de IIC T6 IP65 T 80 °C 

Ex-protection symbol 

Device group II 

Approved for gas 

Approved for dust 

Symbol for equipment built in 

accordance with European standards 

Explosion protection identifier 

Explosion group 

Temperature class 

IP protection class 

Approved maximum temperature

24 



Pressure monitoring in explosion risk 

areas Zone 1, 2 and 21, 22 

Specially equipped pressure switches can also be used in explosion risk areas Zone 1, 2 and 21, 

22. The following alternatives are possible: 

1. Pressure-proof encapsulated switching device, 

explosion protection EEx de IIC T6, PTB 02 ATEX 1121 

The pressure switch with pressure-proof encapsulation can be used directly in the explosion risk area 

(Zone 1 and 2 or 21 and 22). The maximum switching voltage, switching capacity and ambient temperature 

must be taken into account and the rules for installation in the explosion risk area must be 

observed. All pressure switches may be equipped with explosion-proof switching devices. However, 

special circuits and designs with an adjustable switching differential or internal interlock (reclosing lockout) 

are not permitted. 

2. EEx-i pressure switches 

All pressure switches of normal design can be used in explosion risk areas Zone 1 and 2 or 21 and 

22, if they are integrated into an “intrinsically safe control current circuit”. Intrinsic safety is based on 

the principle that the control current circuit in the explosion risk area carries only a small quantity of 

energy which is not capable of generating an ignitable spark. 

Isolating amplifiers, e.g. type Ex 011 or Ex 041, must be tested by the Physikalisch-Technische 

Bundesanstalt (PTB) and approved for use in explosion risk areas. Isolating amplifiers must always be 

installed outside the explosion risk zone. 

Pressure switches designed for EEx-ia installations may be provided with blue connection terminals 

and cable entries. In view of the low voltages and currents carried via the contacts of the microswitches, 

gold-plates contacts are recommended (additional function ZF 513). 

3. Pressure switches with microswitch and resistor combination for short-circuit and line 

break monitoring (see DBS series) 

A combination of a pressure switch with mechanical microswitch connected to a 1.5 kOhm series 

resistor and a safety-engineered isolating amplifier (type Ex 041) may also be used in explosion risk 

zones 1, 2 and 21, 22 (explosion protection EEx-ia). 

The safety-engineered isolating amplifier produces a separate intrinsically safe control current circuit 

and at the same time monitors the supply conductors between the isolating amplifier and the pressure 

switch for short-circuit and line break. In this regard, see also the section on pressure limiters for safety-critical 

applications and data sheet Ex 041. 

Pressure monitoring in explosion risk areas Zone 1 (21) and 2 (22) 

Ex-D… 

Pressure-proof encapsulated 

Explosion protection: EEx de 

IIC T6 PTB approval for the 

complete switching device. 

Switching capacity at 250 V/3 

A. The pressure switch can be 

installed within the Ex-Zone. 

D…-513 + Ex 011 

Intrinsically safe 

Explosion protection: EEx-ia 

PTB approval for isolating 

amplifiers Ex 041 Pressure 

switch with gold-plated contacts, 

blue terminals and blue 

cable entries. 

The isolating amplifier must be 

installed outside the Ex-Zone. 

DWR…-576 + Ex 041 

Intrinsically safe, line break 

and short-circuit monitoring 

Explosion protection: EEx-ia 

PTB approval for isolating 

amplifiers Ex 041 Pressure 

switch with safety sensor, 

positive opening microswitch, 

gold-plated contacts, blue terminals 

and blue cable entries. 

The isolating amplifier must be 

installed outside the Ex-Zone.



25 

10 selection criteria 

CHECKLIST 

1 Medium 

Steam, hot water, fuel gases, air, flue gases, 

liquid gas, liquid fuels, other media 

1a 

Sensor material 

Stainless steel, non-ferrous metals, plastics (e.g. 

Perbunan). Are all sensor materials resistant to the 

medium? Oil and grease-free for oxygen? 

2 Type approval 

Is type approval (TÜV, DVGW, PTB, etc.) required 

for the intended application? 

3 Function 

Monitors, limiters. Safety-engineered 

pressure limiters. 

4 Direction of action 

Is the maximum pressure or minimum pressure to 

be monitored? Does the pressure switch have a 

controller function (e.g. turns pump on and off)? 

5 Setting range 

The desired setting range can be found in the 

Product Summaries. 


6 for controllers/monitors only 

The adjustable switching differential is only important 

in the case of pressure switches with a controller 

function. For limiter functions the switching differential 

(hysteresis) has no significance 

7 Maximum working pressure 

The maximum working pressure listed in the tables 

must be equal to or greater than the maximum 

system pressure 

8 Environmental conditions 

Medium temperature / ambient temperature / type 

of protection / humidity / Ex-zone / Outdoor installation 

– protective measures 

9 Type of construction/Size 


Size, installation position, installation method, pressure 

connection with seal 

10 Electrical data Switching 

capacity 

Switching element / changeover contact / normally 

closed contact / normally open contact / switching 

capacity / interlocking / gold contacts / contactless 

signal transmission 

This list of criteria does not claim to be 

complete. 

However, all items must be checked. 

The stated sequence is expedient but not 

mandatory.

26 




General description 

Operating mode 

The pressure occurring in the sensor housing (1) acts on the measuring bellows (2). Changes in pressure 

lead to movements of the measuring bellows (2) which are transmitted via a thrust pin (4) to the 

connecting bridge (5). The connecting bridge is frictionlessly mounted on hardened points (6). When the 

pressure rises the connecting bridge (5) moves upwards and operates the microswitch (7). A counterforce 

is provided by the spring (8) whose pretension can be modified by the adjusting screw (9) 

(switching point adjustment). Turning the setting spindle (9) moves the running nut (10) and modifies 

the pretension of the spring (8). The screw (11) is used to calibrate the microswitch in the factory. The 

counter-pressure spring (12) ensures stable switching behaviour, even at low setting values. 

1 = Pressure connection 

2 = Measuring bellows 

3 = Sensor housing 

4 = Thrust pin 

5 = Connecting bridge 

6 = Pivot points 

7 = Microswitch or other switching 

elements 

8 = Setting spring 

9 = Setting spindle (switching 

point adjustment) 

10 = Running nut (switching point 

indicator) 

11 = Microswitch calibration 

screw (factory calibration) 

12 = Counter pressure spring 

Pressure sensors 

Apart from a few exceptions in the low-pressure range, all pressure sensors have measuring bellows, 

some made of copper alloy, but the majority of high-quality stainless steel. Measured on the basis of 

permitted values, the measuring bellows are exposed to a minimal load and perform only a small lifting 

movement. This results in a long service life with little switching point drift and high operating reliability. 

Furthermore, the stroke of the bellows is limited by an internal stop so that the forces resulting from 

the overpressure cannot be transmitted to the switching device. The parts of the sensor in contact 

with the medium are welded together without filler metals. The sensors contain no seals. Copper bellows, 

which are used only for low pressure ranges, are soldered to the sensor housing. The sensor 

housing and all parts of the sensor in contact with the medium can also be made entirely from stainless 

steel 1.4571 (DNS series). Precise material data can be found in the individual data sheets. 


The pressure connection on all pressure switches is executed in accordance with DIN 16288 (pressure 

gauge connection G 1/2A). If desired, the connection can also be made with a G 1/4 internal thread 

according to ISO 228 Part 1. Maximum screw-in depth on the G 1/4 internal thread = 9 mm. 

Centring pin 

In the case of connection to the G 1/2 external thread with seal in the thread (i.e. without the usual 

sheet gasket on the pressure gauge connection), the accompanying centring pin is not needed. 

Differential pressure switches have 2 pressure connections (max. and min.) each of which are connected 

to a G 1/4 internal thread.



27 

General technical data 

with microswitches of the DCM, VCM, DNM, DNS and DDC series. 

The technical data of type-tested units may differ slightly. 

(please refer to type sheet) 

Normal version 

Plug connection Terminal connection 

version 

…200 …300 

…700 

Switch housing 


Switching function and connection 

diagram 

(applies only to version with 

microswitch) 

Diecast aluminium GD AI Si 12 Diecast aluminium GD AI Si 12 

G 1/2 external thread (pressure gauge connection) and G 1/4 internal thread 

G 1/4 internal thread for DDCM differential pressure switches 

Floating changeover contact. 

Floating changeover contact. 

With rising pressure switching 

With rising pressure switching 

single-pole from 3-1 to 3-2. single-pole from 3-1 to 3-2. 

Switching capacity 

(applies only to version with 

microswitch) 

Mounting position 

Degree of protection (in vertical 

position) 

Ex degree of protection 

PTB approval Electrical connection 

Cable entry 

Ambient temperature 



Lead seal 

Medium temperature 

Vacuum 

Repetition accuracy of switching 

points 

Vibration strength 

Mechanical life 

Isolation values 

Oil and grease-free 

8 A at 250 VAC 3 A at 250 VAC 

5 A at 250 VAC inductive 2 A at 250 VAC inductive 

8 A at 24 VDC 3 A at 24 VDC 

0.3 A at 250 VDC 0.03 A at 250 VDC 

min. 10 mA, 12 VDC 

min. 2 mA, 24 V DC 

preferably vertical 

vertical 

(see technical data sheet) 

IP 54; (for terminal connection …300 IP 65) IP 65 

– EEx de IIC T6 tested to EN 

50014/50018/50019 (CENELEC) 

– PTB 02 ATEX 1121 

Plug connection to DIN 43 650 (200 series) 


or terminal connection (300 series) 

PG 11 / for terminal connection M 16 x 1.5 M 16 x 1.5 

See data sheets 

–15 to +60°C 

Adjustable via spindle. On switching device 

Adjustable via spindle after the 

300 the terminal box cover must be removed terminal box lid is removed 

Adjustable or not adjustable 

Not adjustable 

(see Product Summary) 

Only possible on plug connection housing 200 

Max. 70°C, briefly 85°C Max. 60°C 

Higher medium temperatures are possible provided the above limits for the switching device are 

ensured by suitable measures (e.g. siphon). 

All pressure switches can operate under vacuum. This will not damage the device. 

< 1% of the working range (for pressure ranges > 1 bar) 

No significant deviations up to 4 g. 

With sinusoidal pressure application and room temperature, 10 x 106 switching cycles. 

The expected life depends to a very large extent on the type of pressure application, therefore this figure 

can serve only as a rough estimate. With pulsating pressure or pressure impacts in hydraulic systems, 

pressure surge reduction is recommended. 

Overvoltage category III, contamination class 3, reference surge voltage 4000 V. 

Conformity to DIN VDE 0110 (01.89) is confirmed. 

The parts of all pressure switches with sensors made from steel or stainless steel are oil and greasefree. 

The sensors are hermetically encapsulated. They contain no seals. (See also additional function 

ZF 1979 Special Packing)

28 



ZF additional functions — Pressure 

switches and pressure monitors 

Example for ordering: 

DWR 6 – 205 

Code of additional function (e.g. maximum limiter) 

Code for pressure range 

Sensor system 

How to order: 

Pressure switch 

DWR 6–205 

or DWR 6 

with ZF 205 

Additional functions / Connection diagrams 

Plug connection Terminal connection Connection diagram Explanation 

200 series (IP 54) 300 series (IP 65) 

Normal version (plug connection) 

Microswitch, single pole switching 

Switching differential not adjustable 

Terminal connection – housing (300) 

…301 

Unit with adjustable switching differential 

ZF 203 

Maximum limiter 

with reclosing lockout 

Interlocking with rising pressure 

ZF 205 

see 

DWR series 

Minimum limiter 

with reclosing lockout 

Interlocking with falling pressure 

ZF 206 

see 

DWR series 

Two microswitches, switching in parallel or in 

succession. Fixed switching interval, only 

possible with terminal connection housing. 

State the switching interval (not possible 

with all pressure switches, see data sheet 

p. 2, pp. 40 - 43) 

ZF 307 * 

Two microswitches, 1 plug switching in 

succession. adjustable switching interval 

Please indicate switching scheme* 

(not possible with all pressure switches, 

see data sheet p. 2, pp. 40 – 43) 

ZF 217 * 

Gold-plated contacts, 

single pole switching (not available with 

adjustable switching differential). 

ZF 213 

Permitted contact 

load: 

Max: 24 VDC,100 mA 

Min: 5 VDC, 2 mA 

Switch housing with surface protection ZF 351 

(chemical version). 

*Switching point adjustment: Please specify switching point and direction of action (rising or falling pressure).



29 

Additional functions 

for EEx-i equipment ZF 5… 

· Housing (300) with terminal connection (IP 65), “blue” cable 

entry and terminals. 

· Also available with resistor combination for line break and 

short-circuit monitoring (with isolating amplifier Ex 041). 

Non-Ex area 

Ex area 

Io Ii 

Uo Ui Pi 

DWAM…-576 

Important: 

All pressure switches with the ZF 5… additional functions listed 

here can only be operated in combination with a suitable 

isolating amplifier (see pages 60 – 61). 

For ZF513, ZF576, ZF574: 

Ui = 15 V DC, Ii = 60 mA, 

Pi = 0.9 W, Ci < 1 nF, Li < 100 μH 

Additional functions for EEx-i equipment Connection diagram Isolating amplifier 

Gold-plated contacts, single-pole ZF 513 Ex 011 

switching. Switching differential fixed (not adjustable). 

Switching capacity: max. 24 VDC, 

100 mA, min. 5 VDC, 2 mA. 

Versions with resistor combination for line break and short-circuit monitoring in control current circuit, see DBS series, pages 54 – 56: 

Normally closed contact with resistor combination ZF 576 Ex 041 

for maximum pressure monitoring, 

gold-plated contacts, 

plastic-coated housing 


Normally closed contact with reclosing lockout ZF 577 Ex 041 

and resistor combination, 

for maximum pressure monitoring 

Plastic-coated housing 


Normally closed contact with resistor combination ZF 574 Ex 041 

for minimum pressure monitoring, 

gold-plated contacts, 

plastic-coated housing 


Normally closed contact with reclosing lockout ZF 575 Ex 041 

and resistor combination, 

for minimum pressure monitoring 



Other additional functions Plug connection Terminal connection 

200 series 300 series 

Adjustment according to customer’s instruction: one switching point ZF 1970* ZF 1970* 

two switching points or defined switching differential ZF 1972* ZF 1972* 

Adjustment and lead sealing according to customer’s instruction: 

one switching point ZF 1971* – 

two switching points or defined switching differential ZF 1973* – 

Labelling of units according to customer’s instruction with sticker ZF 1978 ZF 1978 

Special packing for oil and grease-free storage ZF 1979 ZF 1979 

Documents: Additional documents, e.g. data sheets, operating instructions, TÜV, DVGW or PTB certificates. 

Test certificates according to EN 10 204 

Factory certificate 2.2 based on non-specific specimen test WZ 2.2 WZ 2.2 

Acceptance test certificate 3.1 based on specific test AZ 3.1 AZ 3.1 

Acceptance test certificate for ZFV separating diaphragms AZ 3.1 –V AZ 3.1 –V 

*Switching point adjustment: Please specify switching point and direction of action (rising or falling pressure).

30 



Setting instructions 

Factory calibration of pressure switches 

In view of tolerances in the characteristics of sensors and springs, and due to friction in the switching 

kinematics, slight discrepancies between the setting value and the switching point are unavoidable. 

The pressure switches are therefore calibrated in the factory in such a way that the setpoint adjustment 

and the actual switching pressure correspond as closely as possible in the middle of the range. 

Possible deviations spread to both sides equally. 

The device is calibrated either for falling pressure (calibration at lower switching point) or for rising 

pressure (calibration at higher switching point), depending on the principal application of the type 

series in question. 

Where the pressure switch is used at other than the basic calibration, the actual switching point 

moves relative to the set switching point by the value of the average switching differential. As FEMA 

pressure switches have very small switching differentials, the customer can ignore this where the 

switching pressure is set only roughly. If a very precise switching point is needed, this must be calibrated 

and checked in accordance with normal practice using a pressure gauge. 

1. Calibration at lower switching point 2. Calibration at upper switching point 

Setpoint xS corresponds to the lower 

Setpoint xS corresponds to the upper 

switching point, the upper switching point xO switching point, the lower switching point xU 

is higher by the amount of the switching 

is lower by the amount of the switching differendifferential 

xd. 

tial xd. 

The chosen calibration type is indicated in the technical data for the relevant type series. 

Clockwise: 

lower switching 

pressure 

Anticlockwise: 

higher switching 

pressure 

Setting switching pressures 

Prior to adjustment, the securing pin above the scale must be loosened by not more than 2 turns and 

retightened after setting. The switching pressure is set via the spindle. The set switching pressure is 

shown by the scale. 

To set the switching points accurately it is necessary to use a pressure gauge. 

Direction of action of setting 

spindle 

Clockwise: 

greater 

difference 

Anticlockwise: 

smaller 

difference 

With pressure switches of the 

DWAMV and DWR…-203 series, 

the direction of action of the 

differential screw is reversed. 

Changing the switching differential (only for switching device with suffix “V”, ZF 203) 

By means of setscrew within the spindle. The lower switching point is not changed by the differential 

adjustment; only the upper switching point is shifted by the differential. One turn of the differential 

screw changes the switching differential by about of the total differential range. The switching differential 

is the hysteresis, i.e. the difference in pressure between the switching point and the reset point. 

Lead seal of setting spindle (for plug connection housing 200 only) 

The setting spindle for setting the desired value and switching differential can be covered and sealed 

with sealing parts available as accessories (type designation: P2) consisting of a seal plate and capstan 

screw. The sealing parts may be fitted subsequently. The painted calibration screws are likewise 

covered.


Mechanical pressure switches — Pressure limiters 

31 

Pressure switch with locking of 

switching state (reclosing lockout) 

In the case of limiter functions, the switching state must be retained and locked, and only unlocked 

and the system restarted once the cause of the safety shutdown has been eliminated. There are two 

ways of doing this: 

1. Mechanical locking inside the pressure switch 

Instead of a microswitch with automatic reset, limiters contain a “bistable” microswitch. If the pressure 

reaches the value set on the scale, the microswitch trips over and remains in this position. The lock 

can be released by pressing the unlocking button (identified by a red dot on the scale side of the 

switching device). The interlock can operate with rising or falling pressure depending on the version. 

The device can only be unlocked when the pressure has been reduced (or increased) by the 

amount of the predefined switching differential. When selecting a pressure limiter, it is necessary 

to distinguish between maximum and minimum pressure monitoring. EEx-d versions cannot be 

equipped with internal locking. 

Maximum pressurelimitation 

Minimum pressure limitation 

Switching and interlocking 

with rising pressure. 

Additional function ZF 

205. 

Connection of control 

current circuit to terminals 

1 and 3. 

Switching and interlocking 

with falling pressure. 

Additional function ZF 206. 

Connection of control current 

circuit to terminals 2 

and 3. 

2. External electrical interlock in the control cabinet (suggested circuits) 

A pressure monitor (microswitch with automatic reset) can also be used as a limiter if an electrical 

interlock is added. For pressure limitation in steam and hot water boilers, an external interlock is only 

permitted if it has been ascertained that the pressure monitor is “of special construction”. 

Maximum pressure limitation 

with external interlock 

Minimum pressure limitation 

with external interlock 

Where the above interlock circuit is used, the requirements of DIN 57 116/VDE 0116 are met if the 

electrical equipment (such as contactors or relays) of the external interlock circuit satisfy VDE 0660 or 

VDE 0435.

32 



Explanation of type designations – 

type codes 

The type designations of FEMA pressure switches consist of a combination of letters followed by a 

number denoting the setting range. Additional functions and version variants are indicated by a code 

which is separated from the basic type by a hyphen. Ex versions (explosion protection EEx-d) are identified 

by the prefix “Ex” in front of the type designation. 

Basic version with additional function Ex-version 

(based on the example of DCM series) 

DCM XXX DCM XXX-YYY Ex-DCM XXX 

DCM 

XXX 

YYY 

Ex 

Series code (e.g. DCM) 

Codes for pressure range 

Code for additional functions 

Code for Ex version 

Switch housing version 

DCM XXX 

Basic version with plug connection housing 

DCM XXX-2… 

Basic version with plug connection housing 

DCM XXX-3… Terminal connection housing (300) 

Ex-DCM XXX EEx-d switching device (700) 

DCM XXX-5… 

EEx-i version 

Which additional function goes with which pressure switch? 

Plug connection, 200 series 

Terminal connection, 300 series 



203 213 217 301 307 513 574 575 EEx-d 

576 577 

DCM/VCM • 1 • • 1 • • 1 • • 

VNM/DNS/VNS • • • • • • • 

DWAM • • • • • 

DDCM • • 2 • • 2 • • 

DWR • • • • • • • 

DGM • • • • • • 

• available 1 

except DCM 4016, DCM 4025, VCM 4156 and DCM 1000 

2 

except DDCM 252, 662, 1602, 6002 

Ex-versions (EEx-d) can only be supplied in basic form. 

Additional functions are not possible.



33 

DCM pressure switches 

and pressure monitors 

for overpressure, for non-aggressive 

liquid and gaseous media 

DCM 025 DCM 25 

Technical data 


External thread G 1/2 (pressure gauge connection) 

according to DIN 16 288 and internal 

thread G 1/4 according to ISO 228 Part 1. 

Switching device 

Robust housing (200) made of seawater-resistant 

diecast aluminium GD Al Si 12. 

Degree of protection 

IP 54, in vertical position. 

Pressure sensor materials 

DCM 3…DCM 63 Metal bellows: 1.4571 

Sensor housing: 1.4104 

DCM 025 – DCM 1 Metal bellows: Cu Sensor 

housing: Cu + Ms 

DCM 4016/ Diaphragm: Perbunan 

DCM 4025 Sensor housing: 1.4301 

DCM 1000 Diaphragm: Perbunan 

Sensor housing: Brass 


Vertically upright and horizontal. DCM 4016 

and 4025 vertically upright. 

Ambient temp. at switching device 

–25…+70 °C, except: DCM 4016, 

4025, 1000: –15…+60 °C 

For EEx-d versions: –15…+60 °C 

Max. medium temperature 

The maximum medium temperature at the 

pressure sensor must not exceed the permitted 

ambient temperature at the switching 

device. Temperatures may reach 85°C for 

short periods (not EEx-d). Higher medium temperatures 

are possible provided the above limit 

values for the switching device are ensured by 

suitable measures (e.g. siphon). 

Mounting 

Directly on the pressure line (pressure gaugeconnection) 

or on a flat surface with two 

4 mm Ø screws. 

Switching pressure 

Adjustable from outside with screwdriver. 


Not adjustable with DCM and Ex-DCM types. 

Adjustable from outside with DCM-203 types. 

For values see Product Summary. 

Contact arrangement 

Single-pole changeover switch. 

Switching 250 VAC 250 VDC 24 VDC 

capacity (ohm) (ind) (ohm) (ohm) 

Normal 8 A 5 A 0.3 A 8 A 

EEx-d 3 A 2 A 0.03 A 3 A 

Type Setting range Switching Max. Materials in- Dimendifferential 

permissible contact with sioned 

(mean values) pressure medium drawing 


DCM 4016 1…16 mbar 2 mbar 1 bar Perbunan 1 + 11 

DCM 4025 4…25 mbar 2 mbar 1 bar + 1.4301 

DCM 1000 10…100 mbar 12 mbar 10 bar Perbunan + MS 1 + 10 

DCM 025 0.04…0.25 bar 0.03 bar 6 bar 

DCM 06 0.1…0.6 bar 0.04 bar 6 bar Cu + Ms 1 + 14 

DCM 1 0.2…1.6 bar 0.04 bar 6 bar 

DCM 506 15…60 mbar 10 mbar 12 bar 1 + 12 

DCM 3 0.2…2.5 bar 0.1 bar 16 bar 

DCM 6 0.5…6 bar 0.15 bar 16 bar 

DCM 625 0.5…6 bar 0.25 bar 25 bar 

DCM 10 1…10 bar 0.3 bar 25 bar 1.4104 

1 + 18 

1 + 17 

DCM 16 3…16 bar 0.5 bar 25 bar + 

DCM 25 4…25 bar 1.0 bar 60 bar 1.4571 

DCM 40 8…40 bar 1.3 bar 60 bar 

1 + 16 

DCM 63 16…63 bar 2.0 bar 130 bar 

Switching differential adjustable 

DCM 025-203 0.04…0.25 bar 0.03…0.4 bar 6 bar 

DCM 06-203 0.1…0.6 bar 0.04…0.5 bar 6 bar Cu + Ms 1 + 14 

DCM 1-203 0.2…1.6 bar 0.07…0.55 bar 6 bar 

DCM 3-203 

DCM 10-203 

0.2…2.5 

1…10 

bar 

bar 

0.15…1.5 

0.5…2.8 

bar 

bar 

16 

25 

bar 

bar 

DCM 6-203 

DCM 16-203 

0.5…6 

3…16 

bar 

bar 

0.25…2.0 

0.7…3.5 

bar 

bar 

16 

25 

bar 

bar 1.4104 

1 + 18 

1 + 17 

DCM 25-203 4…25 bar 1.3…6.0 bar 60 bar + 

DCM 40-203 8…40 bar 2.6…6.6 bar 60 bar 1.4571 1 + 16 

DCM 63-203 16…63 bar 3.0…10 bar 130 bar 

For smaller pressure ranges see also VCM, DGM, HCD and DPS sheets. 

For additional functions refer to ZF data sheet. 

version, (housing 700), explosion protection EEx-d 

Ex-DCM 4016 1…16 mbar 2 mbar 1 bar Perbunan 3 + 11 

Ex-DCM 4025 4…25 mbar 2 mbar 1 bar Perbunan 3 + 11 

For other Ex-devices, see type series VCM, DNM, DNS, DDCM, DWR, DGM described below. 

Calibration 

The DCM series is calibrated for falling pressure. This means that the adjustable switching pressure on 

the scale corresponds to the switching point at falling pressure. The reset point is higher by the 

amount of the switching differential. (See also page 30, 1. Calibration at lower switching point). 

s 

Degree of protection: 

IP 54

34 



VCM type series 

Negative pressure switches (vacuum switches) 

VCM 301 

VNM 111 

FEMA negative pressure switches detect the 

pressure difference relative to atmospheric pressure. 

All data relating to the setting range and 

thus also the scale divisions on the switching 

devices are to be understood as the difference 

in pressure between the relevant atmospheric 

pressure and the set switching pressure. 

The “zero” reference point on the scale of the 

unit corresponds to the relevant atmospheric 

pressure. A minus sign before the pressure value 

signifies negative pressure below the relevant 

atmospheric pressure. 







Robust housing (200) made of seawaterresistant 




IP 65, for EEx-d version. 


VNM 111 and Metal bellows: 1.4571 

VNM 301: Sensor housing: 1.4104 

VCM 095, 101 Metal bellows of Cu Zn 

and 301: 

VCM 4156: 

Sensor housing of CuZn 

Perbunan diaphragm sensor 

housing: 1.4301 


Vertically upright and horizontal. 

VCM 4156 vertically upright. 

Ambient temp. at switching device 

–25…+70 °C 





ambient temperature at the switching device. 

Temperatures may reach 85°C for short periods 

(not EEx-d). Higher medium temperatures 

are possible provided the above limit values for 

the switching device are ensured by suitable 

measures (e.g. siphon). 

Mounting 


or on a flat surface with two 





Not adjustable with VCM and Ex-VCM types. 

Adjustable with VCM-203 type. 





Type Setting range Switching Max. Dimendifferential 

permissible sioned 

(mean values) pressure drawing 


VCM 4156 -15…+6 mbar 2 mbar 1 bar 1 + 11 

VCM 301 -250…+100 mbar 25 mbar 1.5 bar 1 + 13 

VNM 301 –250…+100 mbar 45 mbar 3 bar 1 + 15 

VCM 101 –1*…+0.1 bar 45 mbar 3 bar 1 + 14 

VCM 095 –0.9…+0.5 bar 50 mbar 3 bar 1 + 14 

VNM 111 –1*…+0.1 bar 50 mbar 6 bar 1 + 15 


VCM 301-203 –250…+100 mbar 30–200 mbar 1.5 bar 1 + 13 

VNM 301-203 –250…+100 mbar 70 –500 mbar 3 bar 1 + 15 

VCM 101-203 –1*…+0.1 bar 80 –350 mbar 3 bar 1 + 14 

VCM 095-203 –0.9….+0.5 bar 90 –400 mbar 3 bar 1 + 14 

VNM 111-203 –1*…+0.1 bar 90 –650 mbar 6 bar 1 + 15 


Ex-VCM 4156 –15…+6 mbar 2 mbar 1 bar 3 + 11 

Ex-VCM 301 –250…+100 mbar 25 mbar 1.5 bar 3 + 13 

Ex-VNM 301 –250…+100 mbar 45 mbar 3 bar 3 + 15 

Ex-VCM 101 –1*…+0.1 bar 45 mbar 3 bar 3 + 14 

Ex-VCM 095 –0.9…+0.5 bar 50 mbar 3 bar 3 + 14 

Ex-VNM 111 –1*…+0.1 bar 50 mbar 6 bar 3 + 15 

* At very high vacuums, close to the theoretical maximum of –1 bar, the switch may not be usable in 

view of the special conditions of vacuum engineering. However, the pressure switch itself will not be 

damaged at maximum vacuum. 

For additional functions refer to ZF data sheet. 

For smaller pressure ranges see also HCD and DPS data sheets. 

Calibration 

The VCM and VNM series are calibrated for falling pressure. This means that the adjustable switching 

pressure on the scale corresponds to the switching point at falling pressure. The reset point is higher 

by the amount of the switching differential. (See also page 30, 1. Calibration at lower switching point). 




EEx-d 3 A 2 A 0.03 A 3 A 

s 


IP 54/65



35 

DNM type series 

Pressure switches free of non-ferrous metal 

All parts of the DNM series of FEMA pressure 

switches which come into contact with the 

medium are made of stainless steel. The pressure 

sensor is welded according to the latest 

methods without filler metals. 

The diecast aluminium switch housing is also 

highly resistant to aggressive influences in the 

surrounding atmosphere. 

DNM 025 













Sensor housing 1.4104 

Pressure bellows: 1.4571 



Ambient temperature at switching device 

–25…+70 °C. 







short periods (not EEx-d). 

Higher medium temperatures are possible provided 

the above limit values for the switching 

device are ensured by suitable measures 

(e.g. siphon). 






DNM 025 0.04…0.25 bar 0.03 bar 6 bar 1 + 15 


Ex-DNM 10 1…10 bar 0.3 bar 16 bar 3 + 17 

Ex-DNM 63 16…63 bar 1.0 bar 130 bar 3 + 16 

Calibration 

The DNM series is calibrated for falling pressure. This means that the adjustable switching pressure 

on the scale corresponds to the switching point at falling pressure. The reset point is higher by the 


Mounting 

Directly on the pressure line (pressure gauge 

connection) or on a flat surface with two 





Not adjustable with DNM and Ex-DNM types. 






EEx-d 3 A 2 A 0.03 A 3 A 

s 


IP 54/65

36 



DNS type series 

Pressure switch with stainless steel sensor system, with 

optional plastic-coated housing 

DNS 3-201 

Pressure switches of the DNS series are suitable 

for monitoring and controlling pressures in 

chemical plants, process engineering and any 

situation where the pressure of aggressive 

liquids and gases must be monitored. 

All components of the sensor system are made 

from high-quality stainless steel (1.4571) and 

welded using the latest methods without filler 

metals. The pressure sensor is hermetically 

encapsulated and contains no sealing materials. 

DNS 6-351 



External thread G 1/2 (pressure gauge 

connection) according to DIN 16 288 and internal 









Pressure bellows and all parts in contact with 

medium. X 6 Cr Ni Mo Ti 17122 Material no. 

1.4571 



Max. ambient temperature at switching 

device 

–25…+70 °C. 

For EExd versions: –15…+60 °C. 





Temperatures may reach 85°C for short periods 

(not EEx-d). 





Mounting 


or on a flat surface with two 4 mm 

Ø screws. 










EEx-d 3 A 2 A 0.03 A 3 A 

Plastic coating 

The diecast aluminium housing in GD Al Si is 

chromated and stove-enamelled with resistant 

plastic. Corrosion tests with 3% saline solution 

and 30 temperature changes from +10 to 

+80°C showed no surface changes after 20 

days. 






VNS 301-201 -250…+100 mbar 45 mbar 3 bar 

VNS 111-201 -1*…+0.1 bar 50 mbar 6 bar 

DNS 025-201 0.04…0.25 bar 30 mbar 6 bar 1 + 15 

DNS 06-201 0.1…0.6 bar 40 mbar 6 bar 

DNS 1-201 0.2…1.6 bar 60 mbar 6 bar 

DNS 3-201 

DNS 10-201 

0.2…2.5 

1…10 

bar 

bar 

0.1 bar 

0.3 bar 

16 

16 

bar 

bar 

DNS 6-201 

DNS 16-201 

0.5…6 

3…16 

bar 

bar 

0.15 bar 

0.5 bar 

16 

25 

bar 

bar 

1 + 18 

1 + 16 

…-203 types Adjustable switching differential 


VNS 301–351 –250…+100 mbar 45 mbar 3 bar 

VNS 111–351 –1*…+0.1 bar 50 mbar 6 bar 

DNS 025–351 0.04…0.25 bar 30 mbar 6 bar 2 + 15 

DNS 06–351 0.1…0.6 bar 40 mbar 6 bar 

DNS 1–351 0.2…1.6 bar 60 mbar 6 bar 

DNS 3–351 

DNS 10–351 

0.2…2.5 

1…10 

bar 

bar 

0.1 bar 

0.3 bar 

16 

16 

bar 

bar 

DNS 6–351 

DNS 16–351 

0.5…6 

3…16 

bar 

bar 

0.15 bar 

0.5 bar 

16 

25 

bar 

bar 

2 + 18 

2 + 16 


Ex-VNS 301 –250…+100 mbar 45 mbar 3 bar 

Ex-VNS 111 –1*…+0.1 bar 50 mbar 6 bar 

Ex-DNS 025 0.04…0.25 bar 30 mbar 6 bar 3 + 15 

Ex-DNS 06 0.1…0.6 bar 40 mbar 6 bar 

Ex-DNS 1 0.2…1.6 bar 60 mbar 6 bar 

Ex-DNS 3 

Ex-DNS 10 

0.2…2.5 

1…10 

bar 

bar 

0.1 bar 

0.3 bar 

16 

16 

bar 

bar 

Ex-DNS 6 

Ex-DNS 16 

0.5…6 

3…16 

bar 

bar 

0.15 bar 

0.5 bar 

16 

25 

bar 

bar 

3 + 18 

3 + 16 

Explosion protection EEx-i with ZF 513 

Example for ordering: DNS…-513 

* At very high vacuums, close to the theoretical maximum of –1 bar, the switch may not be usable in 

view of the special conditions of vacuum engineering. However, the pressure switch itself will not be 

damaged at maximum vacuum. 

Calibration 

The DNS and VNS series are calibrated for falling pressure. This means that the adjustable switching 

pressure on the scale corresponds to the switching point at falling pressure. The reset point is higher 

by the amount of the switching differential. (See also page 30, 1. Calibration at lower switching point). 

s 


IP 54/65



37 

DDCM type series 

Differential pressure switch 

Ex-DDCM 

DDCM 252 

FEMA differential pressure switches are suitable 

for monitoring and controlling differential pressures, 

flow monitoring and automatic control of 

filter systems. A double chamber system with 

stainless steel bellows or Perbunan diaphragm 

accurately detects the difference between the 

two applied pressures. The desired switching 

pressure is continuously adjustable within the 

ranges mentioned in the type summary. 

The settings relate to the lower switching point 

(with falling differential pressure). The upper 

switching point (with rising differential pressure) 

is higher by the amount of the switching differential. 

All differential pressure monitors can also be 

used in the vacuum range. Every pressure 

switch has 2 pressure connections with appropriate 

markings. 




Internal thread G 1/4 








DDCM 014–16: 

Pressure bellows of 1.4571 

Sensor housing of 1.4305. 

DDCM 252–6002: 

Perbunan diaphragm. 

Aluminium sensor housing. 


vertically upright. 


–25…+70 °C 







short periods (not EEx-d). Higher medium temperatures 

are possible provided the above limit 

values for the switching device are ensured by 

suitable measures (e.g. siphon). 

Mounting 

Directly on the pressure line or on a flat surface 

with two 4 mm Ø screws. 

Note the connection of pressurized lines: 

P (+) = high pressure 

S (–) = low pressure 




Not adjustable. For values see Product 

Summary. 

Scale 

Types 252–6002 without graduation. Set 

according to pressure gauge. 




EEx-d 3 A 2 A 0.03 A 3 A 

Type Setting range Switching Max.** Materials in- Dimen- 

(differential differential permissible contact with sioned 

pressure) (mean values) pressure medium drawing 


DDCM 252* 4…25 mbar 2 mbar 0.5 bar 

DDCM 662* 10…60 mbar 15 mbar 1.5 bar Aluminium 1 + 20 

DDCM 1602* 20…160 mbar 20 mbar 3 bar + Perbunan 

DDCM 6002* 100…600 mbar 35 mbar 3 bar 

DDCM 014* –0.1…0.4 bar 0.15 bar 15 bar 

DDCM 1 0.2…1.6 bar 0.13 bar 15 bar Stainless steel 

DDCM 4* 1…4 bar 0.20 bar 25 bar 1.4305 + 

DDCM 6 0.5…6 bar 0.2 bar 15 bar 1.4571 1 + 21 

DDCM 16 3…16 bar 0.6 bar 25 bar 

* without graduation (only ± scale). For smaller pressure ranges see 

** also loadable on one side also HCD and DPS datasheets. 

Type Setting range Switching Max.** Materials in- Dimen- 

(differential differential permissible contact with sioned 

pressure) (mean values) pressure medium drawing 

version · Explosion protection EEx de IIC T6 

Ex-DDCM 252* 4…25 mbar 2 mbar 0.5 bar 

Ex-DDCM 662* 10…60 mbar 15 mbar 1.5 bar Aluminium 3 + 20 

Ex-DDCM 1602* 20…160 mbar 20 mbar 3 bar + Perbunan 

Ex-DDCM 6002* 100…600 mbar 35 mbar 3 bar 

Ex-DDCM 014* -0.1…0.4 bar 0.15 bar 15 bar 

Ex-DDCM 1 0.2…1.6 bar 0.13 bar 15 bar Stainless steel 

Ex-DDCM 4* 1…4 bar 0.2 bar 25 bar 1.4305 + 3 + 21 

Ex-DDCM 6 0.5…6 bar 0.2 bar 15 bar 1.4571 

Ex-DDCM 16 3…16 bar 0.6 bar 25 bar 

* without graduation (only ± scale) 

** also loadable on one side 

+ 

Accessories: · Threaded joint with male adapter union G 1/4”/8 mm MAU 8/Ms and 

MAU 8/Nst, page 63 

· Valve combinations VKD 3 and VKD 5, page 63 

Calibration 

The DDCM series is calibrated for falling pressure. This means that the adjustable switching pressure 

on the scale corresponds to the switching point at falling pressure. The reset point is higher by the 


s 


IP 54/65

38 



DPS series 

Differential pressure switches for ventilation and air-conditioning 

systems 

Applications 

Differential pressure switches for filter, fan or air 

flow monitoring in air-conditioning and ventilation 

systems. 

DPS 



Plastic connection piece with 6 mm external 

diameter for measuring hose with 5 mm internal 

diameter. Connector P 1 for higher pressure, 

P 2 for lower pressure. 

Pressure medium 

Air, and non-combustible and non-aggressive 

gases. 

Diaphragm 

made of sintered silicone is resistant to outgassing. 

Switching kinematics on the “P2” side. 

Switch housing and parts in contact with 

medium 

Switch housing and pressure connection P 2 

made of PA 6.6. Lower part and pressure connection 

P 1 made of POM. 

Medium and ambient temperature 

–20°C to +85°C 

(storage temperature –40°C to +85°C) 

Maximum working pressure 

50 mbar for all types. 


vertical, pressure connections pointing downwards. 

(With horizontal mounting and cover 

facing upwards, the scale values are 20 Pa 

below the actual values; with horizontal mounting 

and cover facing downwards, the scale values 

are 20 Pa higher. At setting values below 

50 Pa, the device must be mounted vertically!). 

Degree of protection: IP 54 

Mounting 

Via fastening pieces integrated into the housing 

with 2 screws, mounted directly onto a vertical 

surface, e.g. of the airconditioning unit or air 

duct. For mounting in the ceiling area, use an 

L-shaped bracket if necessary. 

Setting the switching point 

Remove the cover and set the scale to the 

desired value. The setting values relating to the 

upper switching point (for maximum pressure 

monitoring). For minimum pressure monitoring, 

the switching point lies below the setting value, 

according to the switching differential. 

Weight: 160 g 

Switching function: single pole switching. 


Flat plug 6.3 x 0.8 

DIN 46 244 or use 

the screw terminals 

supplied. 


Type Setting range for Switching differentials 

upper switching 

(guideline values) 

DPS 200 F 0.2…2 mbar 0.1 mbar 



DPS 1000 F 2…10 mbar 1 mbar 

DPS 2500 F 5…25 mbar 1.5 mbar 

DVGW test certificate 

EC type testing according to EC Gas Appliance Directive (90/396 EEC) and DIN EN 1854, product 

identification number CE-0085AR0013 

+ 

Supplied accessories: 

2 m silicone hose, 2 connection pieces with mounting screws, 

2 self-tapping screws for mounting the housing, 

3 screw terminals for the electrical connection 

+ 

Optional accessories: 

DPSLF L-shaped bracket for installation turned through 90°, e.g. in ceiling area 

DPSJF Channel connection fitting 

Dimensioned drawing 

57.5 

7.5 

18 

8.5 

ÿ4.5 

P2 (low pressure) 

P1 (high pressure) 

Min. switching capacity: 5 mA / 5 VDC 

Max. switching capacity: 1.5 (0.4) A / 250 VAC 

Cable entry: Pg 11 

s 

DVGW 

tested 


IP 54



39 

(according to Gas Appliance 

Directive 90/396/EEC) 

HCD series 

Pressure and differential pressure switches for neutral gases 

(DVGW-tested) 

HCD 

Pressure switches of the HCD series are suitable 

for neutral and non-aggressive gases. They can 

be used for monitoring overpressure and differential 

pressure. For overpressure detection the 

pressure side is connected to the lower connection 

piece G 1/4”; for vacuum detection the 

pressure side is connected to the upper 

connection piece G 1/8” (remove sealing chamber). 

For differential pressure detection the high 

pressure is applied to the lower connection 

piece (G 1/4”) and the low pressure side to the 

upper connection piece (G 1/8”). A pressure 

measurement connector (9 mm ø) is available for 

accurate setpoint adjustment. 



Pressure connection for overpressure: 

G 1/4” internal thread. 

For vacuum and differential pressure: 

G 1/8” internal thread. 

Switch housing 

Diecast aluminium. 

Medium temperature 

–15 to +60 °C. 


See Product Summary 


Horizontal with connection pieces pointing 

downwards. 

Type of protection IP 40 according to DIN 

40050. 

Tested according to Gas Appliance Directive 90/396/EEC, DVGW reg. no. E 3085/2. 

Type Setting range Switching differential Max. 

in lower range in upper range working 

pressure 

HCD 6003 0.2…3 mbar 0.3… mbar 0.5 mbar 100 mbar 

HCD 6010 1…10 mbar 0.3… mbar 1 mbar 100 mbar 

HCD 6050 5…50 mbar 1.5… mbar 3 mbar 200 mbar 

HCD 6150 15…150 mbar 4… mbar 10 mbar 300 mbar 

The switching differential is not adjustable. The low switching differentials are for the lower setting 

range; the higher values relate to the upper ranges. 

Dimensioned drawing 

Mounting 

Either directly on pipe or with mounting bracket 

(supplied) on a vertical surface. 

Setting the switching point 

Remove the cover and turn the setting spindle 

marked +/– in the corresponding direction. 

The scale shows only guideline values. For 

accurate setpoint adjustment it is necessary to 

use a pressure gauge which can be attached 

to the measuring point (9 mm ø pressure 

measurement connector). 

Switching function Single pole switching. 



2 A/220–240 VAC (inductive load) 

10 A/220–240 V AC (resistive load) 

Cable entry Pg 13.5 

s 

GASTEC 

tested 


IP 40

40 


Mechanical pressure switches/Differential pressure switches 

S2 type series 

Pressure switches with 2 microswitches – technical data 

FEMA pressure switches of the DCM (except 

DCM 1000, DCM 4016 and DCM 4025), VCM 

(except VCM 4156), VNM, DNS, VNS series 

and the differential pressure monitor DDCM 

(except DDCM 252, 662, 1602, 6002) can be 

equipped with 2 microswitches (see also the 

table on page 41). 

This is not possible with any other type 

series or with Ex versions. 


Standard equipment 

The standard equipment of every two-stage 

pressure switch includes a switching device 

with 2 microswitches, both single-pole switching. 

Switch I monitors the low pressure, switch 

II the higher pressure. The setting ranges indicated 

in the data sheets for the basic types 

apply to the two-stage pressure switches as 

well. It should be noted that the switching differentials 

of the individual microswitches may 

not be exactly the same due to component tolerances. 

Switching interval 

The switching interval of the two microswitches 

is the difference (in bar or mbar) between 

the switching points of the two microswitches. 

For example: 

When the pressure rises, a two-stage pressure 

switch turns on a warning light (e.g. 2.8 bar), 

and if the pressure continues to rise (e.g. 3.2 

bar) the system shuts down. The switching 

interval is 3.2–2.8 = 0.4 bar. For all versions 

the rule is: 

The switching interval remains constant over 

the whole setting range of the pressure switch. 

If the switching pressure setting is changed 

with the setting spindle, the switching interval 

does not change – the switching points are 

moved in parallel. 


The switching differential, i.e. the hysteresis of 

the individual microswitches, corresponds to 

the values of the relevant basic design referred 

to in the Product Summary. In the case of twostage 

pressure switches, the switching differential 

of the individual microswitches is not 

adjustable. 

Versions 

Two-stage pressure switches are available in 

three different versions, each identified by a ZF 

number. The versions differ in terms of their 

connection schemes and electrical connection 

types (terminal or plug connection). 

The applicable data sheet for the basic types contains the technical data for the two-stage pressure 

switches. This includes all limits of use, temperature, maximum pressure, mounting position, type of 

protection, electrical data etc. The principal dimensions are the same as for single-stage pressure 

switches, with similar pressure ranges and design features. 

Additional Switching inter- Electrical Connection Ordering information 

function val between the connection diagram required 

two microswitches 

ZF 307 

ZF 217 

Factory setting 

according to 

customerspecifications 

Adjustable 

via adjustment 

knobs I and II 

according to 

“Switching intervals” 

table 


(All terminals of both 

microswitches are 

accessible (6 terminals) 

Plug connection 

according to DIN 

43 650 (3-pole + 

ground conductor) 

Function-appropriate 

internal wiring 

according to 

“Switching functions” 

table 

2 x single pole 

switching. 

Example selection 

according to 

“Switching 

schemes” table, 

page 42. 

1. Basic type with ZF 307 

2. Switching points I 

and II, with direction 

of action in each 

case (rising or falling 

pressure). 

Example: DCM 16-307 

Switching point I: 

10 bar falling 

Switching point II: 

12 bar falling or switching 

interval only. 

1. Basic type with 

ZF 217 

2. Switching scheme 

Example: 

DCM 16-217/B 4 

Since all values are 

adjustable within the 

specified limits, no further 

data is required.



41 

S2 type series (selection) 

ZF 217 pressure switches with two microswitches 

and switching intervals 

Switching intervals of two-stage pressure switches (ZF 217, ZF 307) 

Type series 

S2 

ZF 217 

ZF 307 higher pressure lower pressure 

min. switching interval max. switching interval (average values) 

Type Factory Switching scheme Switching scheme Switching scheme 

default A1/A3/B2/B4 A2/A4/C2/C4 B1/B3/D1/D3 

C1/C3/D2/D4 

+ ZF 307 

DCM 06 40 mbar 165 mbar 190 mbar 140 mbar 



DCM 3 0.1 bar 0.65 bar 0.75 bar 0.55 bar 







DDCM 1 0.09 bar 0.55 bar 0.64 bar 0.46 bar 

DDCM 6 0.14 bar 0.94 bar 1.08 bar 0.8 bar 

DNM 025 35 mbar 215 mbar 240 mbar 180 mbar 

VCM 095 40 mbar 300 mbar 340 mbar 260 mbar 



VNM 111 50 mbar 310 mbar 360 mbar 260 mbar 

Switching devices with adjustable switching interval 

Additional function ZF 217 

On switching devices with additional function ZF 217, the switching interval is continuously adjustable 

via two adjustment knobs I and II accessible from outside. The maximum switching intervals are stated 

in the “Switching intervals” table. 

Turning adjustment knob I clockwise produces a lower switching point for microswitch I. 

Turning adjustment knob II anticlockwise produces a higher switching point for microswitch II. 

Adjustment knobs I and II have an internal stop to prevent the microswitches from being adjusted 

beyond the effective range. 

Adding together the adjustments on knobs I and II gives the switching interval between the two 

microswitches. Changes made with the setting spindle do not affect the switching interval. The 

switching interval remains constant over the whole setting range of the spindle. The two switching 

points are moved up or down in parallel. 

Recommended adjustment method for switching devices with ZF 217 

1. Set adjustment knobs I and II to their basic positions. 

Turn adjustment knob I 

as far as possible anticlockwise. 

Turn adjustment knob II 

as far as possible clockwise. 

2. Adjust the setting spindle S by the scale to a value midway between the desired upper and lower 

switching points. 

3. With pressure applied, set the lower switching point with adjustment knob I. 

4. In the same way as in step 3, set the upper switching point with adjustment knob II. 

5. If the desired upper and lower switching points cannot be reached, turn the setting spindle S in the 

appropriate direction and repeat steps 3 and 4.

42 




Two-stage pressure switches, switching schemes for ZF 217 

Function-appropriate internal configuration of microswitches I and II, switching scheme selection table. The switch position shown corresponds 

to the pressureless state. On the horizontal axis is the switching function of microswitch I (A–D); on the vertical axis is the switching 

function of microswitch II (1–4). At the intersection is the switching scheme which satisfies both conditions (e.g. A 2). 

Microswitch I (lower switching point) 

falling, close rising, close falling, open rising, open 

rising, open 

Microswitch II (upper switching point) 

falling, open 

rising, close 

falling, close 

Information required when ordering: 

As well as the basic type (e.g. DCM 10) and the switching scheme (e.g. A 2), for factory setting it is 

also necessary to indicate the switching points and direction of action: 

Example: DCM 10–217 / A 2 Switch I: 6.5 bar falling, Switch II: 7.5 bar rising.



43 


Examples of use for two-stage pressure switches 

Pressure monitoring and controlling can be greatly simplified by using pressure monitors with two 

built-in microswitches which can be made to operate one after the other under rising or falling pressure. 

For example, minimum and maximum pressure monitoring can be achieved with only one pressure 

switch, doing away with the need for a second pressure switch (including the cost of installation). 

Step switching, e.g. pressure-dependent control of a two-stage pump, is of course also possible using 

this special series. 

For pressure-dependent control 

of automatic expansion valves 

and pressure holding devices 

Example 1: 

Requirement 

Pressure holding devices and automatic expansion valves usually have a gas cushion whose pressure 

must be kept constant within a certain range. If the pressure is too low, a compressor is switched on. 

If the pressure is too high, a solenoid valve must be opened to vent the gas. Between these two levels 

is a neutral zone, in which the compressor and the solenoid valve are at rest. 

Solution 

All pressure switches of types DCM, DNM, DNS, each with additional function ZF 217 and switching 

scheme A 2, are suitable. All pressureranges listed in the technical documents are possible. Example 

for ordering: DCM 6-217/A 2 

Switching function / connection scheme 

Switch I: With falling pressure, contact 1–2 closes (compressor on) 

With rising pressure, contact 1 –2 opens (compressor off) 

Minimum and maximum pressure 

monitoring in a nitrogen 

line 

Switch II: 

Example 2: 

With rising pressure, contact 2–3 closes (valve open) 

With falling pressure, contact 2 –3 opens (valve closed). 

In between there is a neutral zone in which the compressor is not switched on 

and the solenoid coil is not energized (off position). 

Requirement 

In a process engineering system, the pressure in a nitrogen line has to be monitored. A green signal 

lamp indicates that the pressure in the line is between 2.2 and 2.6 bar. If the pressure goes below 2.2 

bar or above 2.6 bar, the indicator lamp goes out and the system shuts down. 

Solution 

The first contact of a DCM 3–307 pressure switch with 2 microswitches opens under falling pressure 

at 2.2 bar; the second microswitch opens under rising pressure at 2.6 bar. If the pressure is >2.2 bar 

and 0.9 bar), a yellow signal lamp warns the operator that it is time to change the filter elements. 

If this is not done and the differential pressure rises due to further fouling (e.g. to >1.2 bar), the 

system must be shut down. 

Solution 

A differential pressure switch DDCM 6–307 operates under rising differential pressure (at 0.9 bar), the 

green control lamp goes out; at the same time the yellow lamp comes on (warning that it is time to 

clean the filter). If the differential pressure continues to rise (to >1.2 bar), the circuit opens via 4–6 of 

the second microswitch, the relay drops out and the system shuts down.

44 


Pressure switches of “special design” 

TÜV 

DVGW 

Pressure switches “of special 

construction” 

Definitions and information 

Pressure monitoring and pressure limiting in 

· Steam boilers · Hot water heating systems 

· District heating systems · Gas installations 

· Oil pipelines · Firing systems 

· Liquid gas installations etc. 

is extremely important with regard to safety. 

Component testing 

Pressure monitoring devices for safety-critical applications must work reliably and be tested according 

to the relevant directives in each case. The reliability of pressure monitors and pressure limiters 

must be certified by a component test which is performed by the testing agencies responsible in 

each case (e.g. TÜV and DVGW). The following section deals with the FEMA product range for safety-critical 

pressure monitoring in thermal and process engineering systems. 

Special construction 

The term “of special construction” originates from the VdTÜV Memorandum “Pressure 100/1”, 

issue 04.83, which defines the requirements for pressure monitors and pressure limiters for 

steam boilers and hot water systems. Originally used only for pressure monitoring in the area of 

steam and hot water, the “special construction” characteristic is increasingly used as a quality and 

safety argument for other applications as well. The following section describes the requirements for 

pressure limiters “of special construction”. Recommendations for the correct selection of pressure limiters 

are given by reference to safety analyses. 

Definitions of the VdTÜV Memorandum “Pressure 100/1”: 

Pressure monitors (DW) 

Pressure monitors are devices which switch off the heating system on exceeding and / or falling below a 

predefined pressure limit and release the heating system again only after a change in pressure. 

Pressure limiters (DB) 

Pressure limiters are devices which switch off the heating system on exceeding and / or falling below a 

predefined pressure limit and lock it to prevent automatic restarting. 

Pressure limiters “of special construction” (SDB) 

Pressure limiters “of special construction” perform the same tasks as pressure limiters. In addition they 

must satisfy the extended safety requirements of section 3.3 (of “Pressure 100/1”).


Pressure switches “of special construction” 

45 

Safe condition 

According to DIN VDE 0660, Part 209, the safe condition of the system is reached if a cut-off command 

is present at the output contact which means that in the safe condition, the microswitch in the 

pressure limiter is actuated (opened) and the control circuit is interrupted. Series connected switching 

devices must react in the same way. The operating mode of the safety pressure limitation thus corresponds 

to the closed circuit principle. 

Additional requirements for pressure limiters “of special construction” 

7 

6 

Self-monitoring maximum pressure 

limiter with safety diaphragm 

DWAM…, DWAMV…, SDBAM… 

Pressure limiter without safetydiaphragm 

(not self-monitoring for 

maximum pressure) DWR… 

8 

3 

2 

1 

5 

Section 3.3 of VdTÜV Memorandum “Pressure 100/1”: 

Pressure limiters “of special construction” must, in the event of a breakage in the mechanical 

part of the measuring element, lead to cut-off and interlock of the heating. This requirement is 

also fulfilled if the mechanical part of the measuring element is calculated for vibrating stress or has 

withstood a test with 2 million operating cycles and the pressurized parts of the measuring 

element are made of corrosion-resistant materials. 

(Abbreviated excerpt from VdTÜV Memorandum “Pressure 100/1”). 

Therefore there are two possible ways of meeting the requirements for pressure limiters “of 

special construction”: 

a) By a self-monitoring pressure sensor which is designed so that a breakage in the mechanical part of 

the measuring element leads to cut-off to the safe side (see Fig. 1) 

b) By certification of endurance testing with 2 million operating cycles during the component test (see 

Fig. 2) 

a) Self-monitoring pressure sensor with safety diaphragm 

(for maximum pressure monitoring only) 

Fig. 1 is a cross-sectional diagram of a pressure sensor which fulfils the “special construction” requirements. 

The measuring chamber is bordered by the housing (1), base (2) and measuring bellows (3). All 

parts are made of stainless steel and are welded together without filler metals. When the pressure rises 

the measuring bellows (3) moves upwards, supported by the back pressure spring (5). The setpoint 

spring installed in the switching device acts as a counterforce. A transfer bolt (6) which transfers the 

pressure-dependent movements of the measuring bellows (3) to the switching device located above is 

placed on the inside of the base. A plastic diaphragm (7), which is not in contact with the medium and 

in normal operation follows the movements of the measuring bellows but itself has no influence on the 

position of the bellows, is clamped in the upper part of the transfer bolt. On breakage of the measuring 

bellows (3), the medium can escape into the interior of the bellows. The medium pressure is now on 

the underside of the diaphragm (PL). An additional force is generated because of the far larger effective 

area of the diaphragm compared with the bellows, and this pushes the transfer bolt (6) upwards. This 

results in cut-off to the safe side. The cut-off condition thus achieved is normally interlocked electrically 

or mechanically, so that the system also remains cut off when the pressure drops again. The plastic 

diaphragm (7) is not a pressure-bearing part; it has no function in normal operation and is effective only 

if a leakage occurs to the measuring bellows. Safety diaphragms of the described design are permissible 

up to 32 bar. This should be sufficient for most applications. 

b) Pressure sensors with certification of 2 million operating cycles (DWR series) 

In this design it is assumed that the pressure sensors which have withstood dynamic loading of 2 million 

operating cycles during component testing can be considered as reliable elements. They do not 

have an additional safety device in the sensor. Although the units are produced and tested with very 

great care, maximum pressure limiters without additional safety device can lead to dangerous conditions 

if errors which cannot be detected in the tests occur due to secondary effects. These may be 

caused by hole corrosion due to deposited metal particles on the (usually very thin-walled) bellows of 

the pressure sensor, material defects in the pressure bellows or a broken weld seam. Despite careful 

production and testing, a residual risk remains in the case of maximum pressure monitoring. It is ultimately 

up to the user and operator of the systems themselves to decide on the degree of safety to which 

pressure vessels should be monitored. 

Pressure sensors without safety diaphragm are self monitoring when used in minimum pressure monitoring 

applications.

46 



Safety analysis for maximum 

pressure monitoring 

Observing the direction of action 

The preceding description and safety considerations relate to the monitoring of maximum pressure. 

The safe side here means: The energy supply is cut off (e.g. burner is turned off) to avoid a further 

pressure rise. Minimum pressure monitoring requires an entirely different approach. The safe side here 

means: Preventing the pressure from falling further (for example: hotwater systems with external pressure 

retention or monitoring of water level in heating systems). Based on a safety analysis, a pressure 

limiter without safety diaphragm is clearly the best option. In the event of leakage in the sensor, “low 

pressure” is signalled and the system switches over to the safe side. A pressure sensor without safety 

diaphragmis therefore “of special construction” within the meaning of Memorandum “Pressure 100/1”, 

if it is used as a minimum pressure limiter. On the other hand, it is clear from the above that pressure 

sensors with safety diaphragms, which offer considerable advantages in maximum pressure monitoring, 

should never be used for minimum pressure monitoring. Incorrect use can create a dangerous condition. 

It is therefore essential for users and planners to observe the direction of action when selecting 

pressure limiters. 

In summary it may be said: 

Pressure limiters “of special construction” with safety diaphragms (self-monitoring pressure sensors) 

offer the highest degree of safety in maximum pressure monitoring. Such devices must not however 

be used for minimum pressure monitoring. Pressure limiters “of special construction” with certification 

of 2 million operating cycles are self-monitoring in the case of minimum pressure monitoring, even 

without a safety diaphragm. In the case of maximum pressure monitoring, however, a residual risk 

remains. 

Safety analysis for maximum pressure monitoring 

If one considers the switch positions in the possible operating conditions, the difference compared 

with pressure sensors “of special construction” becomes clear. The left column shows normal operation 

in which the switch connects terminals 3 and 1. The cut-off condition when pressure is too high is 

shown in column 2. The control circuit is interrupted via terminals 3 and 1. 

The difference in safety terms is clear from column 3, which shows the switch position in the event of 

a leak in the pressure sensor. With a safety-engineered sensor the control circuit is interrupted, whereas 

in the case of a sensor without a safety diaphragm the control circuit remains closed, and thus a 

“dangerous condition” can arise. 

Devices with safety diaphragm (DWAM, 

DWAMV, SDBAM) 

In pressure limiters “of special construction” 

which are equipped with safety sensors, 

different operating conditions occur in the 

following switch positions: 

1 

Normal operation 

2 

Limit exceeded 

3 

Leakage in 

pressure sensor 

Control circuit 

closed 


interrupted 


interrupted 

Device without safety diaphragm 

“Special construction” must also be proven by an endurance test with 2 million operating cycles. 

In the case of breakage/leakage (e.g. material defect, fault in weld seams, hole corrosion), the system 

does not cut off to the safe side (no self-monitoring). 

In the different operating conditions the following 

switch positions occur in the case 

of maximum pressure monitoring: In the 

event of leakage in the pressure sensor, the 

pressure monitors/limiters according to b) 

are not safe. A “dangerous condition” can 

arise. 

Normal 

operation 


closed 

Limit 

exceeded 


interrupted 

Leakage in 

pressure sensor 


interrupted Dangerous 

condition!



47 

Further observations and summary 

Minimum pressure 

All minimum pressure monitors and minimum pressure limiters are self-monitoring within the 

meaning of “Pressure 100/1” (with or without safety diaphragm). 

Pressure limiters must interlock the cut-off state 

Memorandum “Pressure 100/1” specifies that pressure limiters must cut off and interlock against automatic 

restarting. For this purpose, pressure limiters are offered with integrated mechanical interlock 

(reclosing lockout). The direction of action is also important in the selection of the interlock. Depending 

on the direction of action it is necessary to determine whether the interlock should operate on rising 

(maximum pressure monitoring) or falling (minimum pressure monitoring) pressure. 

External interlock is also possible 

A pressure monitor can become a pressure limiter if an electrical interlock is connected in series. The 

figures on page 29 show suggested interlock circuits for maximum pressure and minimum pressure 

monitoring. The direction of action must be observed when deciding the circuit. For the combination 

of pressure monitor with external interlock to be considered as a limiter “of special construction”, the 

pressure monitor itself must satisfy the “special construction” requirements. 

Other considerations 

“Special construction” — not just for steam and hot water systems 

According to current standards, pressure limiters “of special construction” are mandatory for steam - 

boilers according to TRD 604 and for heating systems according to DIN 4751 Part 2. They are considered 

to be failsafe elements within the meaning of TRD 604 and can therefore be used on installations 

in 24-hour operation and 72-hour operation (for further information see TRD 604). It is clearly advantageous 

to transfer the positive experience from pressure monitoring of steam boilers to other applications. 

In the interest of greater safety it is desirable to incorporate the requirements for pressure limiters 

“of special construction” used in safety-critical monitoring applications into other standards as 

well. This applies particularly to applications in the field of gas, which are covered by DIN 3398 Parts 1 

and 3, and liquid fuels, covered by DIN 3398 Part 4. 

For even greater safety: 

Positive opening contacts 

In maximum pressure monitoring, safety can be further increased through additional measures. The 

microswitches, normally equipped with a spring contacts, can be fitted with positive opening contacts 

(to protect against contact sticking). 

Line break and short-circuit monitoring 

The power supply to the pressure limiter is monitored for short-circuit and interruption by an external 

isolating amplifier (EX 041). In the case of faults in the power supply, the system cuts off to the safe 

side. EEx-d and EEx-i versions, where applicable combined with sensors “of special construction”, 

open up a wide range of possibilities in the field of Ex applications for process engineering systems 

and gas engineering. See DBS series. 

Summary 

It is apparent that safety can be improved significantly and numerous causes for the occurrence of 

dangerous conditions can be eliminated through the appropriate use of technical measures. However, 

it is also apparent that a residual risk remains. Careful planning and conscientious maintenance and 

testing of existing systems are absolutely essential for reliable pressuremonitoring on pipelines and 

pressure vessels.

48 



Standards – Directives – 

Component tests 

VdTÜV 

Pressure 100/1 

DVGW 

DIN 3398 T.1 and 3 

TÜV 

DIN 3398 T.4 

TÜV, Pressure 100/1 

(DIN 3398 T.3 and 4) 

PED 97/23EC 

ATEX 94/9 EC 

Steam and hot water 

Pressure monitors and pressure limiters for steam and hot water in systems to DIN 4751 T2 and TRD 

604. Series DA and DWR. 

Fuel gases 

Pressure monitors and limiters for fuel gases in accordance with DVGW Worksheet G 260. 

Series DGM and DWR. 

Liquid fuels 

Pressure monitors and pressure limiters for liquid fuels (heating oil) Series DWR. 

Safety-engineered pressure limiters 

For safety-critical pressure monitoring in liquid gas systems, chemical and process engineering systems. 

Pressure Equipment Directive 97/23EC 

Pressure monitors and limiters to DIN 3398 Parts 3 + 4 fall into Category IV of the PED 

-versions 

For Ex areas Zones 1 and 2, all pressure switches can be supplied in pressure-proof encapsulated 

design (Ex degree of protection EEx de IIC T 6). 

PTB approval: PTB 02 ATEX 1121 

For intrinsically safe control circuits (Ex degree of protection EEx-ia), pressure switches with gold contacts,proximity 

switches and the blue terminals and cable entries customary in EExi areas can be supplied. 

In addition to the pressure switch, an isolating amplifier which transfers the control commands of 

the pressure switch from an intrinsically safe control circuit (EEx-ia) to a non-intrinsically safe active circuit 

is required 

Medium 

Steam Hot water 

Fuel gases 

DVGW Worksheet 

G260/1 

Liquid fuels 

(fuel oil) 

Pressure vessels 

(e.g. for 

liquefied gas) 

Plant directives 

DIN 4751 

Part 2 TRD 

604 

Directives for component testing 

VdTÜV 


Issue 4.83 

DIN 3398 

Part 3 

Issue 11.82 

DIN 3398 

Part 4 

Issue 10.86 

TÜV 


DIN 3398 T.4 

Type series 

DA 

DWR… 

DWR… 

DGM… 

DWR… 

FD… 

DWAM…



49 

Selection according to function and 

application 

Application Steam and Fuel gases Heating oil Other 

hot water to DVGW- and other media 

systems to Worksheet liquid 

(check compatibility 

with the materials 

used) 

Function TRD 604 G 260 fuels 

and DIN 4751 T.2 

Pressure monitor 

Pressure monitoring DWAM… DGM… DWR… DWAM… 

Pressure regulation DWAMV… DWR… DWR…-203 DWAMV… 

(e.g. burner or DWR… DWR…-203 DWR… 

pump control) DWR…-203 DWR…-203 

Maximum pressure 

limitation SDBAM… DGM…-205 DWR…-205 SDBAM… 

with internal interlock DWR…-205 DWR…-205 DWR…-205 

with external DWAM… DGM… DWAM… 

interlock DWR… DWR… DWR… DWR… 

Minimum pressure 

limitation DWR…-206 DGM…-206 DWR…-206 DWR…-206 

with internal interlock 

DWR…-206 

with external DWR… DGM… 

interlock DWR… DWR… DWR… 

…The code number for the pressure range must be inserted here (see datasheets). A final number of 

2… (e.g. DWR…-205) means a plug connector according to DIN 43650. 

Pressure limiter with internal 

interlock 

DWR series 

The DWR series covers all the applications mentioned above. 

DA series (self-monitoring sensor) 

DWAM, DWAMV and SDBAM are only suitable for maximum pressure monitoring. They offer 

additional safety due to the safety diaphragm (selfmonitoring sensor). They are TÜV-tested for 

steam and hot water, but thanks to the self-monitoring sensor can also be recommended for other, 

particularly safety-critical applications (e.g. in process engineering). 

Sensors of the DWR series are self-monitoring when used in minimum pressure monitoring applications. 

Equipment of a boiler with pressure 

monitor and pressure limiter 


for burner control: 

DWAM… or DWR… 

(without adjustable switching differential) 

or 

(better, because switching differential 

adjustable) DWAMV… or 

DWR…–203 


DWAM… 

or DWR… 

Pressure limiter 

SDBAM… or 

DWR…-205 

Pressure limiter for 

safety monitoring: 

SDBAM… or DWR…–205 

(with internal interlock, unlocking 

button on the pressurelimiter) 

or 

DWAM… or DWR… (with external 

interlock in the control cabinet) 

Suggested connection for the 

external interlock, see page 31.

50 



DA series 

Maximum pressure monitors and limiters 

DWAM 1 




to DIN 16 288 and internal thread G 1/4 to 

ISO 228 Part 1. 


Rugged housing (200) made of seawaterresistant 

diecast aluminium. 

Materials 

Pressure bellows: Material no. 1.4571 

Sensor housing: Material no. 1.4104 

Switch housing: GD AI Si 12 

according to DIN 1725 




–20 to +70°C. 

Medium temperature –20 to +70°C. 




Temperatures may reach 85°C for short periods. 

Higher medium temperatures are possible 

provided the upper limit at the switching device 

is ensured by suitable measures (e.g. siphon). 

Mounting 




Calibration for maximum pressure switch 

The pressure monitors and safety pressure limiting 

devices are calibrated so that, under rising 

pressure, switching takes place at the defined 

switching pressure. The reset point under 

falling pressure is lower by the amount of the 

switching differential, or, in the case of pressure 

limitingdevices, by the fall in pressure specified 

in the table. The scale value corresponds to the 

upper switching point. 


See Product Summary. 






Sealing P2 

Generally available for SDBAM limiters. 

Bursting pressure 

For all types 100 bar. 

Verified by TÜV test. 

Component tested for 

Testing basis 

TÜV type test approval mark 

Function 


Sensor 

Steam Systems according to TRD 604 

Hot water Systems according to DIN 4751, T. 2 

VdTÜV Memorandum “Pressure 100/1” 

TÜV · DW 04 – 132 for series DWAM… 

TÜV · DW 04 – 133 for series DWAMV… 

TÜV · SDB 04 – 134 for series SDBAM… 

Pressure monitor / Pressure limiter 

For maximum pressure monitoring only 

“Of special construction” (self-monitoring sensor with 

safety diaphragm) 

Product Summary Maximum pressure monitoring ( ) (for other pressure ranges see DWR series) 




Pressure monitors without differential adjustment for max. pressure monitoring 

DWAM 06 0.1…0.6 bar 0.04 bar 5 bar 

DWAM 1 0.2…1.6 bar 0.05 bar 5 bar 

DWAM 6 1.2…6 bar 0.2 bar 10 bar 

DWAM 625 1.2…6 bar 0.25 bar 20 bar 

DWAM 16 3…16 bar 0.4 bar 20 bar 

DWAM 32 6…32 bar 1.2 bar 45 bar 

Pressure monitors with differential adjustment for max. pressure monitoring 

DWAMV 1 0.2…1.6 bar 0.12…0.6 bar 5 bar 

DWAMV 6 1.2…6 bar 0.4…1.5 bar 10 bar 

DWAMV 16 3…16 bar 0.8…2.5 bar 20 bar 

DWAMV 32 6…32 bar 2.5…6.0 bar 45 bar 

Pressure limiters for maximum pressure monitoring (with internal interlock) 

Pressure change 

for unlocking 

SDBAM 1 0.2…1.6 bar 0.12 bar 5 bar 

SDBAM 2,5 0.4…2.5 bar 0.15 bar 5 bar 

SDBAM 6 1.2…6 bar 0.4 bar 10 bar 

SDBAM 625 1.2…6 bar 0.6 bar 20 bar 

SDBAM 16 3…16 bar 0.8 bar 20 bar 

SDBAM 32 6…32 bar 3.0 bar 45 bar 

TÜV 

TESTED 

1 + 15 

1 + 19 

1 + 15 

1 + 19 

1 + 15 

1 + 19 

The maximum permissible working pressure is defined as the upper limit at which the operation, 

switching reliability and water tightness of the pressure switch are in no way impaired. Pressure monitors 

DWAM… can also be used for maximum pressure limitation if an external interlock is used (see 

page 31). 

s 

tested 


IP 54



51 

DWR series 

Pressure monitors for steam and hot water, 

fuel gases and liquid fuels 

DWR 625 




to DIN 16 288 and internal thread G 1/4 

to ISO 228 Part 1 (for gas applications internal 

thread permissible only up to 4 bar). 




Materials 


Sensor housing: Material no. 1.4104 Switch 

housing: GD AI Si 12 (DIN 1725) 


Vertically upright and horizontal. In Ex version 

only vertical. 


–25 to +70°C, 

for EEx-d version –15 to +60°C. 

Medium temperature –25 to +70°C. The maximum 

medium temperature at the pressure sensor 

must not exceed the permitted ambient temperature 

at the switching device. Temperatures may 

reach 85°C for short periods (not EEx-d). Higher 

medium temperatures are possible provided the 

above limit values for the switching device are 

ensured by suitable measures (e.g. siphon). 

Mounting 

Directly on the pressure line (pressure gauge connection) 

or on a flat surface with two 4 mm Ø screws. 

Calibration 

The DWR series is calibrated for rising pressure. 

This means that the adjustable switching pressure 

on the scale corresponds to the switching point at 

rising pressure. The reset point is lower by the 

amount of the switching differential. (See also 

page 30, 2. Calibration at upper switching point). 

In version ...-203 the switching differential is 

adjustable. The basic calibration is maintained. 

Bursting pressure 

For all types 100 bar, verified by TÜV test. 

Switching differential For values see Product 

Summary. 

Contact arrangement Single pole changeover 

switch. 




EEx-d 3 A 2 A 0.03 A 3 A 

Degree of protection IP 54 according to DIN 

40 050 

IP 65 (alternative version) 

Ex protection 

EEx de IIC T6, approval PTB 02 ATEX 112, 

EEx-i with ZF 513 

Degree of protection of EEx-d version 

IP 65, installation position only vertical. 


Testing basis 

Pressure 100/1, Issue 4.83 

DIN 3398, T. 3, Issue 11.92 

DIN 3398, T. 4, Issue 10.86 

Function 


Sensor 


Type Setting range Switching Maximum Dimendifferential 

working pressure sioned 

(mean values) 1* 2* drawing 

Pressure monitors without differential adjustment 

DWR 06 0.1…0.6 bar 0.04 bar 6 bar 6 bar 1 + 15 

DWR 1 0.2…1.6 bar 0.06 bar 

DWR 3 0.2…2.5 bar 0.1 bar 10 bar 16 bar 1 + 18 

DWR 6 0.5…6 bar 0.2 bar 

DWR 625 0.5…6 bar 0.25 bar 20 bar 25 bar 1 + 17 

DWR 16 3…16 bar 0.5 bar 

DWR 25 4…25 bar 1.0 bar 50 bar 63 bar 1 + 16 

DWR 40 8…40 bar 1.3 bar 

EEx-ia versions with ZF 513 (page 29) 


DWR 06–203 0.1…0.6 bar 0.08…0.5 bar 6 bar 6 bar 1 + 15 

DWR 1–203 0.2…1.6 bar 0.15…0.6 bar 

DWR 3 –203 0.2…2.5 bar 0.17…1.2 bar 10 bar 16 bar 1 + 18 

DWR 6 –203 0.5…6 bar 0.3…1.4 bar 

DWR 625 –203 0.5…6 bar 0.4…2.5 bar 20 bar 25 bar 1 + 17 

DWR 16 –203 3…16 bar 0.75…3.15 bar 

DWR 25 –203 4…25 bar 1.3…6.0 bar 50 bar 63 bar 1 + 16 

DWR 40–203 8…40 bar 2.3…6.6 bar 

-versions (EEx de IIC T6) e.g. for fuel gases (housing 700) 

Ex-DWR 06 0.1…0.6 bar 0.04 bar 6 bar 6 bar 3 + 15 

Ex-DWR 1 0.2…1.6 bar 0.06 bar 

Ex-DWR 3 0.2…2.5 bar 0.1 bar 10 bar 16 bar 3 + 18 

Ex-DWR 6 0.5…6 bar 0.2 bar 

Ex-DWR 625 0.5…6 bar 0.25 bar 20 bar 25 bar 3 + 17 

Ex-DWR 16 3…16 bar 0.5 bar 

Ex-DWR 25 4…25 bar 1.0 bar 50 bar 63 bar 3 + 16 

Ex-DWR 40 8…40 bar 1.3 bar 

* max. working pressure Column 1: For devices according to DIN 3398, Part 3 (gas pressure 

monitors) 

Column 2: For devices according to “Pressure 100/1” and DIN 3398, 

Part 4 (for steam, hot water and liquid fuels) 

s 

tested 



Fuel gases DVGW Worksheet G 260 

Liquid fuels 

e.g. fuel oils 

Registration no. 

ID: 000 000 7042 

NG-4347AQ1411 

3 C028/05 

Pressure monitor or pressure limiter 

(with external interlock) 

For maximum and minimum pressure 

monitoring (DWFS, SDBFS) 

“of special construction” by testing with 2 million cycles. 

DVGW 

TÜV 

TÜV 

DVGW 


IP 54/65

52 



DWR-B series 

Pressure limiters for steam and hot water, 

fuel gases and liquid fuels 

DWR 625-205 

The pressure limiters are equipped with a reclosing 

lockout for the mechanical interlocking of the 

switch-off state. If the switching point set on the 

pressure limiter is reached, the limiter switches 

off. The switch-off state is retained even if the 

pressure changes again. It can only be reset by 

manually operating the reset button. For unlocking 

to be possible, the pressure at the sensor 

must have fallen (in the case of maximum pressure 

limiters) or risen (in the case of minimum 

pressure limiters). The pressure change values 

are listed in the Product Summary. 




to DIN 16 288 and internal thread G 1/4 to 

ISO 228 Part 1 (for gas applications internal 

thread permissible only up to 4 bar). 




Materials 


Sensor housing: Material no. 1.4104 

Switch housing: GD AI Si 12 (DIN 1725) 

Mounting position Vertically upright and horizontal. 


–25…+70°C 


Testing basis 

Pressure 100/1, Issue 4.83 

For maximum pressure limiter 

For minimum pressure limiter 

DIN 3398, Part 3, Issue 11.92 

DIN 3398, Part 4, Issue 10.86 

Function 




Fuel gases DVGW Worksheet G 260 

Liquid fuels 

e.g. fuel oils 

Registration no. 

TÜV.SDB.02 – 310 

TÜV.SDB.02 – 309 

NG-4347AQ1411 

3 C028/05 

Pressure limiter (with internal interlock) 

TÜV 

DVGW 

For maximum and minimum pressure monitoring (SDBFS) 

Medium temperature –25…+70°C. 

The medium temperature at the pressure sensor 

must not exceed the permitted ambient temperature 

at the switching device. Temperatures may 

reach 85°C for short periods. 





Mounting 




Calibration 

The DWR-205 series is calibrated for rising pressure. 

This means that the adjustable switching 

pressure on the scale corresponds to the switching 

point at rising pressure. The reset point is 

lower by the amount of the switching differential. 

(See also page 30, 2. Calibration at upper 

switching point). The DWR-206 series is calibrated 

for falling pressure. This means that the 

adjustable switching pressure on the scale corresponds 

to the switching point at falling pressure. 

The reset point is higher by the amount of 

the switching differential. (See also page 30, 

1. Calibration at lower switching point). 

Bursting pressure For all types 100 bar, 

verified by TÜV test. 

Switching differential For values see Product 

Summary. 

Contact arrangement Single pole changeover 

switch. 




Degree of protection IP 54 according to DIN 

40 050 

IP 65 (alternative version) 

Sealing P2 

On request (can be fitted later). 

Sensor 

“Of special construction” by testing with 2 million cycles. 

Important: When selecting the limiter, it is necessary to decide whether the device is to be 

used for maximum or minimum pressure monitoring. The direction of action cannot be 

reversed at the pressure limiter. 


Type Setting range Switching Maximum Connection 

differential working pressure diagram 

(mean values) 1* 2* 

Maximum pressure limiters 

DWR 06–205 0.1…0.6 bar 0.06 bar 6 bar 6 bar 

DWR 1–205 0.2…1.6 bar 0.09 bar 

DWR 3 –205 0.2…2.5 bar 0.20 bar 10 bar 16 bar 

DWR 6–205 0.5…6 bar 0.30 bar 

DWR 625 –205 0.5…6 bar 0.50 bar 20 bar 25 bar 

DWR 16 –205 3…16 bar 0.70 bar 

DWR 25 –205 4…25 bar 1.4 bar 50 bar 63 bar 

DWR 40–205 8…40 bar 2.3 bar 

Minimum pressure limiters 

DWR 06–206 0.1…0.6 bar 0.06 bar 6 bar 6 bar 

DWR 1 –206 0.2…1.6 bar 0.09 bar 

DWR 3 –206 0.2…2.5 bar 0.20 bar 10 bar 16 bar 

DWR 6–206 0.5…6 bar 0.30 bar 

DWR 625 –206 0.5…6 bar 0.50 bar 20 bar 25 bar 

DWR 16 –206 3…16 bar 0.70 bar 

DWR 25 –206 4…25 bar 1.4 bar 50 bar 63 bar 

DWR 40–206 8…40 bar 2.3 bar 

* Maximum working pressure and dimensions as for type series DWR. Pressure monitors DWR… 

(page 51) can also be used as maximum pressure and minimum pressure limiters with external interlock. 

You will find other maximum pressure limiters with safety sensor, type series SDBAM…, on page 

50. Types DWAM… can also be used with external interlock as maximum pressure limiters. 

s 

tested 

DVGW 

TÜV 


IP 54/65



53 

FD series 

Safety-engineered maximum pressure limiter 

for liquid gas systems, setting range 5 –16 bar 

FD 

Pressure limiters of the FD series are constructed 

in accordance with the special directives for 

liquid gas engineering. The requirements of TRB 

801 Appendix II §12 are met. All parts coming 

into contact with the medium are made of stainless 

steel 1.4104 and 1.4571. The parts of the 

sensor subjected to pressure are welded without 

filler metals. Over and above the requirements of 

the TRB, the pressure sensor is “self-monitoring”, 

i. e. in the event of rupture of the measuring 

bellows, the pressure limiter switches off to the 

safe side. The pressure sensor thus complies 

with the “special construction” requirements as 

defined in the VdTÜV Memorandum “Pressure 

100/1”. 


Pressure connection External thread G 1/2 (pressure 

gauge connection) according to DIN 16 288. 

Switch housing 300 

Diecast aluminium GD Al Si 12. 

Degree of protection: IP 65 

Explosion protection EEx-ia (only when used 

in conjunction with Ex 041 isolating amplifier). 

TÜV testing station identifying mark see 

Product Summary. 


Housing: 1.4104, Pressure bellows: 1.4571 

All parts fully welded. Perbunan safety 

diaphragm (not in contact with medium). 

Ambient temperature –25°C to +60°C. 

At ambient temperatures below 0°C, ensure 

that condensation cannot occur in the sensor 

or in the switching device. 

Max. medium temperature: +60°C. 

Outdoor installations 

Protect the device against direct atmospheric 

influences. Provide a suitable protective cover. 

Max. permissible working pressure: 40 bar. 

Switching pressure: 5–16 bar. Adjustable 

with the setting spindle after removing the terminal 

box. 

Calibration 

The FD16-316 and FD16-327 series are calibrated 

for rising pressure. This means that the 

adjustable switching pressure on the scale corresponds 

to the switching point at rising pressure. 

The reset point is lower by the amount of 

the switching differential. (See also page 30, 

2. Calibration at upper switching point). 

Mounting 

Can be fitted directly onto pressure line with 

suitable weld-on connections and union nuts. 

Interlock after cutout 

Internal interlock on FD 16–327. 

Interlock defeat: after pressure reduction of 

approx. 2.5 bar by pressing the red button (with 

tool) on the scale side of the pressure switch. 

External interlock on FD 16–326. 

Interlock defeat: After pressure reduction of 

approx. 0.5 bar. Press unlocking button in control 

cabinet. 

Line break and short-circuit monitoring 

On types FD 16–326 and FD 16–327 used in 

conjunction with Ex 041 isolating amplifier, the 

control circuit is monitored for short-circuit 

and line break. The resistor combination incorporated 

into the pressure switch ensures that 

a defined current flows at all times during normal 

operation. In the event of short-circuit or 

line break, the current level changes and the 

relay drops out to the safe side. 

The pressure limiters are used in intrinsically safe control circuits (Ex protection EEx-ia). Through use of 

the Ex 041 isolating amplifier and a suitable resistor combination in the switching device of the pressure 

limiter, the control circuit is monitored for line break and short-circuit. 


Type Setting Switching Inter- Periphery TÜV-testing Dimensional 

range differential lock* station identifying drawing 

FD 16 –326 5-16 bar 0.5 External Isolating amplifier 

01-12-0109 1 + 19 

Ex 041, 

(self-monitoring with 

FD 16 –327 5-16 bar 2.5 Internal line break and 01-12-0110 1 + 19 

short-circuit monitoring) 

* Interlock on reaching upper cutoff point (maximum pressure set). 

Defeat: 

E = External, i.e. in control cabinet via relay with latching 

I = Internal, i.e. locally at pressure limiter 

For technical data of isolating amplifier, see Datasheet Ex 041, page 61. 

Please note when ordering: List pressure limiter and isolating amplifier separately. 

Internal circuit 

s 

tested 

FD 16 –326 

Single-pole changeover switch with resistor combination 

for line break and short-circuit monitoring. 

(External interlock in control cabinet necessary). 

FD 16 –327 

Single-pole changeover switch with mechanical 

switching state interlock on reaching maximum 

pressure and with resistor combination for line break 

and short-circuit monitoring. 

Please note: FD pressure limiters must never be connected directly to mains voltage. They 

must only be used in conjunction with isolating amplifier Ex 041. 


IP 54

54 



DBS series 

Pressure monitors and limiters 

for especially safety-critical applications 

DWAM…-576 


Greater safety 

· in process engineering and chemical 

installations, 

· in gas and liquid gas installations 

Basic features: 

– “Of special construction” according to VdTÜV 

Memorandum “Pressure 100/1” 

– Line break and short-circuit monitoringbetween 

pressure switch and isolating amplifier 

EX 041 

– Suitable for Ex areas (zone 1 & 2 or 21 & 22) 

(explosion protection EEx-ia) 

– Degree of protection IP 65 

– Plastic-coated housing (chemical version) 

Options: 

– Limiter with internal interlock 

Type-specific features: 

– Self-monitoring sensors 

– Positive opening microswitches 

– Gold-plated contacts 

– TÜV, DVGW component tests 

Safety-engineered pressure limiters offer a higher degree of safety compared with normal pressure 

switches and are therefore especially suitable for chemical process engineering and thermal installations 

in which safety is an especially critical factor in pressure monitoring. The pressure switches can 

also be used in Ex zones (zone 1, 2 and 21, 22) and in all cases require an Ex 041 isolating 

amplifier. The isolating switching amplifier is also responsible for monitoring lines for short-circuit and 

line break and therefore offers an additional safety advantage — even in non-Ex zones. 

For Ex applications, the isolating amplifier must be installed outside the Ex zone. 

The lines between the Ex 041 isolating amplifier and the pressure switch are monitored for short-circuit 

and line break. 

Safety requirements for pressure limiters 

Pressure limiters “of special construction” (DBS) must fulfil additional safety requirements, i.e. breakage 

or leakage in the mechanical part of the sensor must lead to shutdown to the safe side. The pressure 

limitermust respond as if the system pressure had already exceeded the maximum limit. The control 

circuit for the pressure limiter must also be considered from the point of view of safety, as short-circuits 

in the supply lines or other faults in the control current circuit can lead to dangerous conditions. 

Switching element with positive opening operation and gold-plated contacts 

The microswitch is equipped with positive opening operation. Rather than transmitting the plunger 

force via a spring, which is the usual method with most microswitches, this newly developed 

microswitch has an additional lever which transmits the movements of the pressure bellows positively 

to the contact lever. If the spring breaks, the contact lever is moved directly. 

Line break and short-circuit monitoring in the control circuit 

The resistor connected in series with the switching contact limits the current to a defined value with 

the switch closed. In the event of short-circuit in the area between the isolating amplifier and the series 

resistor, the current rises above the predetermined limit value, the relay of the isolating amplifier drops 

out, the output current circuit is interrupted and thus the safe condition is achieved. In the event of a 

line break, the current flow isinterrupted, the relay drops to the safe side and interrupts the output current 

circuit (safety sequence). Furthermore, the isolating amplifier is designed so that, if faults occur in 

the electronics (conductor interruption, component defect etc.) and in the resulting situations, the safe 

shutdown condition is assured. These characteristics of the safety-engineered isolating amplifier, 

including line break and short-circuit monitoring, satisfy the requirements of DIN/VDE 0660, Part 209. 

Connection diagram 

See also Datasheet Ex 041. For pressure monitoring in Ex areas, the isolating amplifier must be 

installed outside the Ex zone. The pressure limiter has an intrinsically safe control current 

circuit (EEx-ia). This arrangement is suitable for zones 1 and 2, 21 and 22.



55 

Safety-engineered maximum 

pressure monitors 




according to DIN 16 288. 

Switch housing 500 

Diecast aluminium GD AI Si 12. 

Aluminium housing coated with 

resistant plastic. 

Degree of protection IP 65. 

Ex protective category 

EEx-ia (only when used in conjunction with 

Ex 041 isolating amplifier). 

Component testing See table on page 56. 


Housing: 1.4104 

Pressure bellows: 1.4571 

All parts fully welded. 

Ambient temperature –25°C to +60°C. 

At ambient temperatures at or below 0°C, ensure 

that condensation cannot occur in the sensor or 

in the switching device. 

Max. temperature of medium at sensor + 

60°C. 

Outdoor installations 

Protect the device against direct atmospheric 

influences. Provide a protective cover. 

Max. working pressure 


Switching pressure setting 

Adjustable with the setting spindle after 

removing the terminal box. 

Mounting 

With suitable weld-on connections and union 

nuts or with pressure gaugescrew union G 1/2. 


24 VDC, max. 100 mA. (at higher switching 

power the gold plating on the contact may be 

damaged). 

Connection diagrams 

…576 

…577 

Maximum pressure monitors 

Sensor “of special construction”, self-monitoring via safety diaphragm, type-tested according to 

VdTÜV Memorandum “Pressure 100/1”. 

Type Setting range Switching differential Max. permissible 

(mean values) 

pressure 

DWAM 06-576 0.1…0.6 bar 0.04 bar 5 bar 

DWAM 1-576 0.2…1.6 bar 0.05 bar 5 bar 

DWAM 2.5-576 0.4…2.5 bar 0.07 bar 5 bar 

DWAM 6-576 1.2…6 bar 0.15 bar 10 bar 

DWAM 625-576 1.2…6 bar 0.25 bar 20 bar 

DWAM 16-576 3…16 bar 0.4 bar 20 bar 

DWAM 32-576 6…32 bar 1.2 bar 45 bar 

Versions: 

ZF 577: Maximum pressure limiter (with internal interlock) Microswitch not positive opening, 

contacts: silver alloy. Other equipment as for DWAM…576 

Ex 041 isolating amplifier, see page 61. 

Maximum pressure monitors 

Sensor “of special construction” through component test with 2 million operating cycles (not selfmonitoring). 

Component tests: 

VdTÜV Memorandum “Pressure 100/1” 

DIN 3398 T.3 (for fuel gases) 

DIN 3398 T.4 (for liquid fuels) 

Type Setting range Switching Max. permissible pressure 

differential in other 

(mean values) gas media 

DWR 06-576 0.1…0.6 bar 0.04 bar 6 bar 6 bar 



DWR 6-576 0.5…6 bar 0.2 bar 10 bar 16 bar 


DWR 16-576 3…16 bar 0.5 bar 20 bar 25 bar 



Versions: 

ZF 577: Maximum pressure limiter (with internal interlock) 

Microswitch not positive opening, contacts: silver alloy. Other equipment as for DWR…576 


Calibration 

Devices of the DWR-576 and DWAM-576 series are calibrated for rising pressure. This means that 

the adjustable switching pressure on the scale corresponds to the switching point at rising pressure. 

The reset point is lower by the amount of the switching differential. (See also page 30, 2. Calibration at 

upper switching point). 

s 

tested 

DVGW 

TÜV 


IP 65

56 



Safety-engineered minimum pressure monitors 

for maximum and minimum pressure monitoring 


Switching element 

See table opposite. 

Connection diagrams 

…574 …575 

The other technical data correspond to the 

devices for maximum pressuremonitoring 

(page 55). 

Type Setting range Switching Max. permissible pressure 

differential in other 

(mean values) gas media 









Calibration 

The DWR-574 series is calibrated for falling pressure. This means that the adjustable switching pressure 

on the scale corresponds to the switching point at falling pressure. The reset point is higher by 

the amount of the switching differential. (See also page 30, 1. Calibration at lower switching point). 

Versions: 

ZF 575: Minimum pressure limiter (with internal interlock) 

Microswitch not positive opening, 

Switching contacts: silver alloy 

Other equipment as for DWR…574 


Features of safety-engineered pressure monitors 

and pressure limiters 

Devices Component testing Features Options 

1 = VdTÜV Memorandum “Pressure 100/1” 

2 = DIN 3398 Part 3 

3 = DIN 3398 Part 4 

Resistor combination for line break and 

short-circuit monitoring 

EExi version for intrinsically safe 

control circuits 

Self-monitoring pressure sensor 

Positive opening microswitches 

Gold-plated contacts 

Limiter with internal interlock 

(reclosing lockout) 


Chemical version 


FD 16-326 1 + 3 • • • • • 

FD 16-327 1 + 3 • • • • 

DWAM…576 1 • • • • • • 

DWAM…577 1 • • • • • 

DWR…576 1 + 2 + 3 • • • • • 

DWR…577 1 + 2 + 3 • • • • 


DWR…574 1 + 2 + 3 • • • • • • 

DWR…575 1 + 2 + 3 • • • • •


DVGW-tested mechanical pressure switches 

57 

DGM series 

Pressure monitors for fuel gases 

DGM 310 A 



External thread G 1/2 to DIN 16 288 and internal 

thread G 1/4 to ISO 228 Part 1 (permissible 

up to 4 bar). 


Seawater-resistant diecast aluminium 

GD AI Si 12. 


IP 54 for vertical installation position. 

IP 65 (for EEx-d version) 


Testing basis 

Function 


DVGW Reg. No. 

CE Ident. No. 

Fuel gases according to DVGW Worksheet G 260 

DIN 3398, Part 3, Issue 11/82, DIN EN 1854 

Pressure monitor, pressure limiter 

Pressure monitor (with internal or 

external interlock) 

For maximum and minimum 

pressure monitoring 

NG-4346 AP 1011 CE-0085 AQ 1088 

DVGW 

(according to 

Gas Appliance 

Directive 

90/396/EEC) 



Ambient temperature –25 to +60°C. 

–15 to +60°C (for EEx-d versions). At ambient 

temperatures below 0°C, ensure that condensation 

cannot occur in the sensor or in the 

switching device. 



Mounting 

Either directly on the pipe or with 

two 4 mm ø screws on the wall surface. 



EEx-d version only vertical. 

Setting 

Continuously adjustable via the setting spindle 

with a screwdriver. The set switching pressure 

is visible in the scale window. 

Sealing P2 

On request (can be fitted later). 

Switching differentials 

Largely independent of the set switching pressure. 

Not adjustable. For values see Product 

Summary. 




EEx-d 3 A 2 A 0.03 A 3 A 

Switching devices in EEx-i version with goldcontacts. 

Max. switching capacity: 24 VDC 100 mA. 

Pressure measuring connection 

Care must be taken to ensure that a pressure 

measuring connection is available in a suitable 

place on the gas appliance. 


Type Setting range Switching Max. Materials Dimendifferential 

working in contact sioned 

(mean values) pressure with medium drawing 

DGM 306 A 15…60 mbar 6 mbar 0.8 bar CU + Ms 

DGM 310 A 20…100 mbar 7 mbar 0.8 bar CU + Ms 1 + 13 

DGM 325 A 40…250 mbar 10 mbar 0.8 bar CU + Ms 

DGM 06 A 100…600 mbar 25 mbar 2 bar CU + Ms 1 + 14 

DGM 1 A 0.2…1.6 bar 40 mbar 3 bar CU + Ms 

DGM 506 15…60 mbar 8 mbar 5 bar 1.4104 

DGM 516 40…160 mbar 12 mbar 5 bar 1.4104 1 +12 

DGM 525 100…250 mbar 20 mbar 5 bar 1.4104 

For other pressure ranges see type series DWR 

-versions Degree of protection EEx de IIC T6, housing 700 

Ex-DGM 506 15…60 mbar 10 mbar 5 bar 1.4104 

Ex-DGM 516 40…160 mbar 12 mbar 5 bar 1.4104 3 + 12 

Ex-DGM 525 100…250 mbar 20 mbar 5 bar 1.4104 


EEx-i version (intrinsically safe) Housing 500 

DGM 306-513 15…60 mbar 6 mbar 0.8 bar CU + Ms 

DGM 310-513 20…100 mbar 7 mbar 0.8 bar CU + Ms 2 + 13 

DGM 325-513 40…250 mbar 10 mbar 0.8 bar CU + Ms 

DGM 06-513 100…600 mbar 25 mbar 2 bar CU + Ms 2 + 14 

DGM 1-513 0.2…1.6 bar 40 mbar 3 bar CU + Ms 

DGM 506-513 15…60 mbar 10 mbar 5 bar 1.4104 

DGM 516-513 40…160 mbar 12 mbar 5 bar 1.4104 2 + 12 

DGM 525-513 100…250 mbar 20 mbar 5 bar 1.4104 

Calibration 

The DGM series is calibrated for rising pressure. This means that the adjustable switching pressure on 

the scale corresponds to the switching point at rising pressure. The reset point is lower by the amount 

of the switching differential. (See also page 30, 2. Calibration at upper switching point). 


s 

tested 

DIN 

tested 

DVGW 

tested 


IP 54/65

58 



Dimensioned drawings of switch housings 

1 

Housing 200 (plug connection) 

2 

Housing 300 and 500 (terminal connection) 

FORM A 

3 

Housing 700 (Ex) 

Dimensioned drawings of pressure sensors 

10 

11



59 

Dimensioned drawings of pressure sensors 

12 13 

14 15 

16 19 

SW 

Dimensioned 

drawing 

SW 

16 22 

17 24 

18 30 

19 32 

20 21

60 


Accessories 

Accessories for EX 011 series 

Isolating amplifier for intrinsically safe control circuits 

· 1-channel 

· Control circuit EEx-ia IIC 

· Reversible direction of action 

· 1 signal output with 1 change-over 

· EMC according to NAMUR NE 21 

Application 

Suitable for all pressure and temperature switches 

with microswitches (basic versions) and for 

devices with additional function ZF 513: 

EX 011 


Ex area 

Nominal voltage 230V, 45 Hz…65 Hz 

Power consumption 1 W 

Input (intrinsically safe) Terminals 1+, 3– 

Nominal data according to DIN 19234 

No-load voltage/short-circuit current 

approx. 8 VDC/approx. 8 mA 

Switching point 1.2 mA…2.1 mA 

PTB approval PTB 00 ATEX 2081 

Explosion protection EEx-ia 

Outputs (not intrinsically safe) 

Contact load 

AC: 250V/2 A/cos. > 0.7 

DC: 240V/1 A resistive load 

Switching frequency 10 Hz 

Electrical isolation 

Input/output 

according to DIN EN 50 020, safely electrically 

isolated. 

Input/mains 

according to DIN EN 50 020, safely electrically 

isolated. 

Output/mains according to DIN EN 50 178 

Ambient temperature –20°C…+60°C 

With the type EX 011 isolating amplifier intrinsically safe control circuit commands can be transmitted 

to non-intrinsically safe active circuits. The inputs are safely isolated from the outputs and from the 

mains in accordance with DIN EN 50 178. 


The direction of action of the outputs can be adjusted with the slide switch S1 on the front of the 

housing. 


The direction of action of the output can be 

adjusted with the slide switch S1 on the front 

of the housing. 

Control circuit Output relay LED 

yellow 

red 

LED 

green = mains 

yellow = relay output 

red = line break 

Slide switches 

S1 Direction of action 

S2 No function 

Mounting 

Standard rail 35 mm. 

Dimensions 

20 x 115 x 93 (W x H x D). 

Switching contact closed picked up on off 

Switching contact open dropped out off off 

The table applies to switch position S1 = OFF 

Type designation 

Type Supply voltage Power consumption 

EX 011 230V, 45…65 Hz 1 W 

s


Accessories 

61 

Accessories for EX 041 series 

for intrinsically safe control circuits with short-circuit 

and line break monitoring 

EX 041 

· 1-channel 

· 1 failsafe relay output 

according to DIN VDE 0660 Part 209 

(BIA certificate no. 940 64) 

· Control circuit EEx-ia IIC 

· 1 progressive output with 1 normally open 

contact 

· 1 passive electronic output, error message 

Application 

Suitable for all safety-engineered pressure monitors/pressure 

limiters, with microswitches and 

resistor combination 

ZF 576 ZF 574 ZF 577 ZF 575, 

FD series 


Nominal voltage 230V, 48 Hz…62 Hz 

Power consumption 3 W 

Input (intrinsically safe) Terminals 10+, 12– 

No-load voltage/short-circuit current 

approx. 8.4 VDC/approx. 11.7 mA 


Relay dropped out J < 2.1 mA and J > 5.9 mA 

Relay picked up 3.2 mA < J < 5mA 

Line resistance 

< 50 ohm. Cable capacitances and inductance 

must be taken into account in the Ex area. 

PTB approval PTB 00 ATEX 2043 

Explosion protection, category EEx-ia 

Outputs (not intrinsically safe) 

Output I: (failsafe) 

Relay terminals 13, 14 

Output II: (not failsafe) 

Relay terminals 15, 21 

Contact load 

AC: 250V/1 A/cos. > 0.7 

DC: 24V/1 A resistive load 

Output III 

Error message (not failsafe) 

Electronic output, passive, terminals 16+, 17– 

Nominal voltage DC 10 V…30 V 

Nominal current < 7 mA, short-circuit-proof 

Switching frequency 5 Hz 

Ambient temperature –20°C…+60°C 

Installation Standard rail 35 mm. 

Dimensions 

40 x 115 x 93 (W x H x D). 

The type EX 041 isolating amplifier is used for the transmission of intrinsically safe control commands 

(e.g. from pressure switches) to non-intrinsically safe active circuits. In the event of short-circuit 

or line break in the control circuit, the isolating amplifier switches to the safe side (see 

“Direction of action” table). It also reacts to the safe side (output relay drops out) if internal component 

failures and resultant errors occur. 

Output I Relay output failsafe according to VDE 0660, Part 209, terminals separately led to the 

outside for series connected protective interlock circuit, for example. 

Output II Progressive output with relay stage (not failsafe). 

Output III Alarm output potential-free (not failsafe). 

Important note 

The type EX 041 isolating amplifier can only be used together with pressure switches with resistor 

combination (additional function ZF 576, ZF 577…, see also “Application” above). 


Control circuit Output relay Status indicator Electronic 

I and II yellow red output III 

Switching contact closed picked up on off blocked 

Switching contact open dropped out off off blocked 

Line break or short-circuit dropped out off on switched 

in the input circuit 

through 

Contact welding dropped out off on switched 

Output I 

through 

Type designation 

Type Supply voltage Power consumption 

EX 041 230 V, 48…62 Hz 3 W 

s

62 


Accessories 

Accessories for ZFV series 

Pressure mediators attached to pressure switches 

A separating diaphragm or a pressure mediator 

is necessary if aggressive, viscous or crystallizing 

media must be kept away from the actual pressure 

sensor. A pressure mediator is also indispensable 

to avoid cavities if easy cleaning of the 

supply lines is important. Special “milk pipe 

unions” according to DIN 11 851 are customary 

for pressure monitoring in the foodstuffs industry. 

Pressure mediators and evaluating devices 

(pressure switches, pressure transmitters, pressure 

gauges) from a self-contained unit. The 

transmission fluid (filling medium) transmits the 

medium pressure from the separating membrane 

to the measuring element. The filling 

medium M 20 is food-safe and, being able to 

withstand temperatures from –40 to +300°C, is 

also suitable for industrial applications. 


Material 1.4571. 

Realization 

Fully assembled, evacuated, filled 

and adjusted. 

Filling medium M 20, food-safe. 

Max. permissible pressure 

40 bar (applies to separating diaphragm only. 

The max. permissible pressure of the pressure 

switch or pressure transmitter must be 

observed). 


DN Switching point from Temperature range* Type 

Flanged pressure mediators made of stainless steel 1.4571, membrane flush to the front, flange to DIN 2527 

50 0.3 bar –40…120°C ZFV 184-50 

80 0.15 bar ZFV 184-80 

with Teflon coating 

50 0.3 bar –40…120°C ZFV 184-50PTFE 

80 0.15 bar –40…120°C ZFV 184-80PTFE 

Flanged pressure mediators with 1 m pipeline, flange to DIN 2527 

50 0.3 bar –30…300°C ZFV 185-50 

80 0.15 bar ZFV 185-80 


50 0.3 bar –30…300°C ZFV 185-50PTFE 

80 0.15 bar –30…300°C ZFV 185-80PTFE 

Pipeline up to a maximum of 10 m on request 

Technical information 

Combinations with pressure mediators are filled and calibrated at 20°C. Very different operating temperatures 

can adversely affect the measurement result, particularly with long capillary pipes and large 

flange diameters. Furthermore, all capillary pressure mediators must be filled and adjusted at the 

same height as the evaluation unit. If the measuring points and the evaluation units are at different 

heights within the system, any pressure difference must be taken into account when setting the 

switching points. This effect is particularly noticeable when monitoring small system pressures. 

DN Switching point from Temperature range* Type 

Pressure mediators for the foodstuffs industry with milk pipe connection according to DIN 11851 

50 0.4 bar –30…120°C ZFV 162-50 


50 0.4 bar –30…120°C ZFV 162-50PTFE 

Screw-in pressure mediators flush to the front 

G 1 0.6 bar –30…120°C ZFV 749 

* Please note that the temperature at the pressure switch must not exceed 60°C for long periods. 

Note: 

In future, all pressure switches purchased together with ZFV must be ordered in the following way: 

e.g. DCM 6-S + ZF 1970 

+ ZFV 184-50


Accessories 

63 

Accessories 

Siphons, NPT adapters, pressure surge reducers 

U-shape (Form B) 

Circular (Form D) 

according to DIN 16282 made of seamless steel tube 20 mm ø 

FORM B Material Type 

Inlet: Weld-on end with weld chamfer St 35.8-I U 430 B 

Outlet: Connection shank DIN 16 282 Form 6 1.4571 U 480 B 

G 1/2” with clamping sleeve DIN 16 283 G 1/2“ 

FORM D Material Type 

NPT1 

Inlet: Weld-on end with weld chamfer St 35.8-I K 430 D 

Outlet: Connection shank DIN 16 282 Form 6 1.4571 K 480 D 

G 1/2” with clamping sleeve DIN 16 283 G 1/2“ 

NPT adapter 

The purpose of the NPT adapter is to connect pressure switches, pressure transmitters, pressure 

gauges etc. to NPT threaded connections. A suitable sealing washer is also supplied. 

DMW-K 

Description 

Type 

NPT adapter, material 1.4104 and sealing ring NPT 1 

DIN 16 258, Form C material ITC to DIN 3754 Part 1 

Pressure surge reducer 

Medium Material Type 

Water and gaseous media Brass DMW 

Water and gaseous media Brass DMW-K 

Accessories 

Threaded joints and valve combinations for differential pressure 

VKD 3 

MAU 8 / Ms 

MAU 8 / Nst 

VKD 5 

Threaded joint with male adapter union G 1/4”/8 mm 

G 1/4” external thread with O-ring seal for connection of pipes with 8 mm external diameter for connection 

of: 

Differential pressure switches DDCM… and other devices with G 1/4” internal thread 


Body O-ring Type 

Brass NBR MAU 8 / Ms 

Stainless steel (1.4571) FPM MAU 8 / Nst 

Max. permissible temperature: 100°C Max. permissible pressure: 100 bar 

Valve combinations for differential pressure switches 

The valve blocks are suitable for differential pressure switches DDCM 014 to DDCM 16 

and for differential pressure transmitters FHBN... 


Pressure stage: PN 420 

Materials: Housing 1.4404 

Internal parts 1.4571 

Seals: 

PTFE 

Process connections: 1/4–14 NPT 

Included items: Supplied complete with screw fittings and shaped pipe 

sections in stainless steel. 


Type 

3-fold combination VKD 3 

5-fold combination VKD 5 

The 5-fold combination contains two additional venting valves.

64 


Specifications 


Pressure switches/isolating amplifiers 

Type series Pressure switches 

PST… Electronic pressure switches for liquid and gaseous media with 2 

open collector switching outputs and analogue output, power supply 

14…36V DC, type of protection IP 65, switching points freely 

adjustable from … to … bar. Freely programmable analogue output 

4–20 mA or 0–10 V (may also be inverted), process connection G 

3/4‘‘ or G 1/2‘‘, absolute or relative pressure versions 

Type: PST… 

PST…R Electronic pressure switches for liquid and gaseous media with 2 

open collector switching outputs, analogue output and potential-free 

relay output, power supply 14…36V DC, type of protection IP 65, 

switching points freely adjustable from … to … bar. Freely programmable 

analogue output 4–20 mA or 0–10 V (may also be inverted), 

process connection G 3/4‘‘ or G 1/2‘‘, absolute or relative pressure 

versions 

Type: PST…R 

DCM… Pressure switch with plug connection to DIN 43650. Switch housing 

made of diecast aluminium GD Al Si 12, type of protection IP 54. 

Range of adjustment from ... to ... bar/mbar. Switching differential 

adjustable / not adjustable. Pressure connection G 1/2, external and 

G 1/4, internal 

Type: DCM… 

DNM…/ Pressure switch with plug connection to DIN 43650. Sensor housing 

VNM… made of stainless steel 1.4104. Switch housing made of diecast aluminium 

GD Al Si 12, type of protection IP 54. Range of adjustment 

from ... to ... bar/bar. Switching differential adjustable / not 

adjustable. Pressure connection G 1/2, external and G 1/4, internal 

Type: DNM... 

DNS…/ Pressure switch with plug connection to DIN 43650. Sensor made 

VNS… entirely of stainless steel 1.4571. Switch housing made of diecast 

aluminium GD Al Si 12, type of protection IP 54. Range of adjustment 



Type: DNS...,VNS... 

DNS...351/ Pressure switch with terminal connection. Sensor made entirely of 

VNS...351 stainless steel 1.4571. Switch housing made of diecast aluminium 

GD Al Si 12, plastic-coated housing, type of protection IP 65. Range 

of adjustment from ... to ... bar/bar. Switching differential adjustable / 

not adjustable. Pressure connection G 1/2, external and G 1/4, internal 

Type: DNS…, VNS… 

DDCM 252… Differential pressure switch with plug connection to DIN 43650. 

DDCM 6002 Sensor made of aluminium, measuring diaphragm of Perbunan. 

Pressure connection G 1/4, internal, switch housing made of diecast 

aluminium GD Al Si 12, type of protection IP 54. Range of adjustment 

from …to…bar/bar 

Type DDCM... 

DDCM 1… Differential pressure switch with plug connection to 

DDCM 16 DIN 43650 Sensor made of stainless steel 1.4104 and 1.4571. 

Pressure connections G 1/4, internal. Switch housing made of 

diecast aluminium GD Al Si 12, type of protection IP 54. Range of 

adjustment from …to …bar/bar 

Type: DDCM…Type series 

DWAM…/ Pressure monitor “of special construction” for maximum pressure 

DWAMV… monitoring with self-monitoring sensor (safety sensor). Tested 

according to VdTÜV Memorandum “Pressure 100/1”. Switch housing 

made of diecast aluminium GD Al Si 12, plug connection to DIN 

43650, type of protection IP 54. Range of adjustment from ... to ... 

bar/bar. Switching differential adjustable / not adjustable. Pressure 

connection G 1/2, external and G 1/4, internal 

Type: DWAM… 

SDBAM… Pressure limiter “of special construction” for maximum pressure monitoring. 

With internal interlock (reclosing lockout) with self-monitoring 

sensor (safety sensor), tested according to VdTÜV Memorandum 

“Pressure 100/1”. Switch housing made of diecast aluminium GD Al 

Si 12, plug connection to DIN 43650, type of protection IP 54. Range 

of adjustment from ... to ... bar/mbar. Pressure connection G 1/2, 

external and G 1/4, internal 

Type: SDBAM… 

DWR…/ Pressure monitor “of special construction” for maximum and 

DWR…203 minimum pressure monitoring. Tested according to VdTÜV 

Memorandum “Pressure 100/1” and DIN 3398 Part 3 and Part 4. 

Switch housing made of diecast aluminium GD Al Si 12, plug connection 

to DIN 43650, type of protection IP 54. Range of adjustment 



Type: DWR… 

Type series Pressure switches 

DWR…205/ Pressure limiter “of special construction” for maximum pressure (205) 

DWR…206 or minimum pressure monitoring (206). With locking of switching 

state (reclosing lockout). Tested according to VdTÜV Memorandum 

“Pressure 100/1” and DIN 3398 Part 3 and Part 4. Switch housing 

made of diecast aluminium GD Al Si 12, plug connection to DIN 

43650, type of protection IP 54. Range of adjustment from ... to ... 

bar/bar. Pressure connection G 1/2, external and G 1/4, internal 

Type: DWR… 

DGM… Pressure monitor for gas with plug connection to DIN 43650. DVGWtested 

according to DIN 3398, Parts 1 and 3. Sensor casing of 

Cu/Zn/high grade steel 1.4104. Switch housing of diecast aluminium 

GD Al Si 12, plug connection to DIN 43650, type of protection IP 54. 

Range of adjustment from ... to ... bar/bar. Switching differential not 


Type: DGM… 

DWAM…576 Pressure monitor “of special construction” for maximum pressure 

monitoring. With self-monitoring sensor (safety sensor), positive 

opening contacts (gold-plated). Resistor combination for wire break 

and short-circuit monitoring. Tested according to VdTÜV 

Memorandum “Pressure 100/1”. Switch housing made of diecast aluminium 

GD Al Si 12, type of protection IP 65. Range of adjustment 

from ... to ... bar/bar. Pressure connection G 1/2, external and G 1/4, 

internal 

Type: DWAM…576 

FD 16 –326 Pressure monitor “of special construction” for maximum pressure 

monitoring in liquid gas systems with self-monitoring sensor (safetysensor). 

Resistor combination for wire break and short-circuit monitoring. 

TÜV-tested according to VdTÜV Memorandum “Pressure 

100/1” and DIN 3398, Part 4. Explosion protection: EEx-i. Switch 

housing made of GD Al Si 12, type of protection IP 65. Adjustable 

from 3 to 16 bar. Pressure connection G 1/2, external and G 1/4, 

internal 

Type: FD 16 –326 

FD 16 –327 Pressure limiter “of special construction” for maximum pressure monitoring 

in liquid gas systems with self-monitoring sensor(safety-sensor). 

Switching state interlock (reclosing lockout). Resistor combination 

for wire break and short-circuit monitoring. TÜV-tested according 

to VdTÜV Memorandum “Pressure 100/1” and DIN 3398, Part 4. 

Explosion protection: EEx-i. Switch housing made of GD Al Si 12, 

type of protection IP 65. Adjustable from 3 to 16 bar. Pressure connection 

G 1/2, external and G 1/4, internal 

Type: FD 16-327 

Type series 

Ex 011 

Ex 041 

Isolating amplifier 

Isolating amplifier for intrinsically safe control circuits. Explosion protection: 

EEx-ia IIC. Signal output: 1 change-over, nominal voltage 

230 V, 45 –60 Hz 

Type: Ex 011 

Safety-engineered isolating amplifier for intrinsically safe control circuits. 

Explosion protection: EEx-ia IIC. Signal output: 1 failsafe relay 

output, nominal voltage 230 V, 45 –60 Hz, type of protection IP 65 

Type: Ex 041 

The specifications refer to the listed normal versions of the pressure switches. In the 

case of Ex versions or devices with additional functions, the texts must be supplemented 

or amended accordingly.

Pressure transmitters

66 

Pressure transmitters 

Overview 

Pressure and differential pressure transmitters/ 

Electrical pressure switches/transmitters 

Type series Pressure ranges Medium Output signal Operating Remarks/ Page 

mode 

Applications 

F Vacuum up to 40 bar liquid and 0–10 V Mechanical- For general 67 – 73 

Differential pressure gaseous 0–20 mA inductive applications in 

up to 10 bar 4–20 mA liquid and 

Operating ranges (3-conductor gaseous media. 

continuously 

system) 

adjustable 

PST -1…600 bar liquid and 0–10 V Piezoresistive Electronic 6 – 17 

gaseous 10–0 V pressure switches 

stainless steel 4–20 mA with configurable 

sensors 20–4 mA transmitter 

2-channel 

output 

switch 

SN Up to 60 bar liquid and 0–10 V / Piezoresistive Highly accurate 74 – 78 

Operating ranges gaseous 4–20 mA Hermetically encontinuously 

(stainless steel (3-conductor-system) capsulated sensor 

adjustable sensors) 4–20 mA system made of 

(2-conductor-system) 

stainless steel. 

DPT Differential pressure gaseous 0–10 V / Piezoresistive Ventilation and 79 

-50 Pa/+50 Pa 4–20 mA air-conditioning 

up to 0–2500 Pa (3-conductor-system) systems 

4–20 mA 

(2-conductor-system) 

Accessories 80 – 82 

Specifications 83



67 

Type series F 

Pressure transmitters, mechanical-inductive 

Operating method 

Pressure transmitters are used to convert overpressure, 

vacuum or differential pressure into a 

proportional electrical signal of 0–10 V, 0–20 mA 

(4–20 mA). A metal bellows or diaphragm is 

exposed to the occurring pressure. The pressure-dependent 

movements of the metal bellows 

are transmitted free of play to an inductive displacement 

sensor. The electronic system converts 

the position of the displacement sensor 

into a proportional electrical signal (voltage and 

injected current). 

General technical information 

Operating principle 

Cover 

Evaluation 

module 

ED 1 

Sensor 

module 

with terminal 

box 


connection 

A complete transmitter consists 

of a sensor module with pressure 

and electrical connections, 

an evaluation module and a 

cover. 

Type series F…+ ED 1 F…+ ED 3 

Electrical connection Terminal connection Plug connection 

Additional evaluation modules can 

be plugged in. 

Voltage output characteristic 

Output signal 

Output signal 

0–10 V and 0–20 mA 0–10 V 

Current output characteristic

68 


for overpressure, vacuum, differential pressure 

Type series F…+ ED 1 

with terminal connection 

Pressure FN… + ED 1 

Differential pressure FHBN…+ ED 1 

Pressure transmitter with 3 conductors 

· with 2 output signals 0–10 V and 0–20 mA 

· Switchable to 2–10 V and 4–20 mA 

and invertible 

· Plug-in display module AZ 331 

Pressure transmitters of the F series produce 

0–10 V / 0–20 mA. Both signals are applied to 

the terminal strip and can be used in parallel. A 

complete transmitter consists of a sensor parts 

and the plug-in evaluation module ED 1. 

Removing the cover gives access to an operator 

interface for adjusting the operating range. 

A plug-in digital display AZ 331 is available to 

display the output signal in any units 

(voltage / current / pressure / differential 

pressure). For further details see Datasheet AZ. 

Characteristic of a transmitter 

(nominal range) 


Operating range Smallest Max. Sensor Type 

(nominal range) adjustable permissible material 

P0–PN operating range pressure 

(approx. values) 

Overpressure 

0 – 50 mbar 20 mbar 2.5 bar FN 505 + ED 1 

0 – 100 mbar 25 mbar 5 bar FN 510 + ED 1 

0 – 250 mbar 65 mbar 6 bar 1.4104 FN 025 + ED 1 

0 – 500 mbar 125 mbar 6 bar + FN 05 + ED 1 

0 – 1 bar 250 mbar 6 bar 1.4571 FN 1 + ED 1 

0 – 2.5 bar 0.7 bar 16 bar FN 3 + ED 1 

Vacuum 

–1 to 0 bar 250 mbar 6 bar 1.4104 FVN 111 + ED 1 

–1 to 1 bar 500 mbar 6 bar + FVN 112 + ED 1 

–1 to 5 bar 1.5 mbar 25 bar 1.4571 FVN 105 + ED 1 

–250 to+250 mbar 125 mbar 3 bar FVN 125 + ED 1 

Differential pressure 

0 – 500 mbar 125 mbar 10 bar FHBN 05 + ED 1 

0 – 1 bar 250 mbar 15 bar 1.4305 FHBN 1 + ED 1 

0 – 2.5 bar 0.7 bar 15 bar + FHBN 3 + ED 1 

0 – 5 bar 1.25 mbar 15 bar 1.4571 FHBN 5 + ED 1 

0 – 10 bar 2.5 mbar 25 bar FHBN 10 + ED 1 

+ 

Accessories 


· Programmable display APV 630 

For differential pressure 

· Valve combination VKD 3, VKD 5 

· Threaded joint with male adapter union MAU 8 

i 

Note 

· If measured values diverge due to higher static (system) pressure, observe the adjustment instructions 

on page 71. 

s 


IP 65


for overpressure, vacuum, differential pressure 

69 

Type series F…+ ED 3 

with plug connection 

FN… 

· Openable plug connection is easy to fit and 

service, with a transparent front 

· 0–10 V output (invertible) 


Pressure and differential pressure transmitters of 

the F…+ ED 3 series (with voltage output) are 

almost identical to versions …ED 1. A voltage 

signal is available at the connection plug. 

Possible settings are described on pages 71 – 

72. 

FHBN… 

Characteristic ED 3 


Operating range Smallest Max. Sensor Type 

(nominal range) adjustable permissible material 

P0–PN operating range pressure 

(approx. values) 

Overpressure 

0 – 50 mbar 20 mbar 2.5 bar FN 505 + ED 3 


0 – 250 mbar 65 mbar 6 bar + FN 025 + ED 3 


0 – 1 bar 250 mbar 6 bar FN 1 + ED 3 

0 – 2.5 bar 700 mbar 16 bar FN 3 + ED 3 

Vacuum 


–1 to +1 bar 500 mbar 6 bar + FVN 112 + ED 3 


–250 to +250 mbar 125 mbar 3 bar FVN 125 + ED 3 

Differential pressure 

0 – 500 mbar 125 mbar 10 bar FHBN 05 + ED 3 

0 – 1 bar 250 mbar 15 bar 1.4305 FHBN 1 + ED 3 

0 – 2.5 bar 0.7 bar 15 bar + FHBN 3 + ED 3 

0 – 5 bar 1.25 bar 15 bar 1.4571 FHBN 5 + ED 3 

0 – 10 bar 2.5 bar 25 bar FHBN 10 + ED 3 

+ 

Accessories 


For differential pressure 

· Valve combination VKD 3, VKD 5 

· Threaded joint with male adapter union MAU 8 

i 

Note 

· If measured values diverge due to higher static (system) pressure, observe the adjustment instructions 

on page 71. 

s 


IP 65

70 


Type series F 


All plugged-in modules are powered 

via the terminal strip of the 

sensor module (on ED 1) or via the 

plug connection. The output signal 

is sent from each module for further 

evaluation via the same route. 

The power consumption increases 

by approx. 1 W for each additional 

module plugged in. 

Connection schemes 


Supply voltage 

24 V AC ± 20% or 24–36 V DC 

Signal and supply voltage is connected to the sensor module. 

Power consumption 

max. 1 W 

Outputs (short-circuit proof) 0–10 V, 2–10 V (± 1 mA), 

0–20 mA, 4–20 mA (3-conductor system) 

All outputs are invertible. 

Load impedance 

max. 750 Ohm. 


Rising pressure produces a rising output signal (default setting). 

Invert with slide switch 4. 

Output signal 

Voltage and current output can also be picked up and used 

0–10 V and 0–20 mA simultaneously. Terminals 5–8 are reserved for later expansions 

and must not be connected as this would destroy the device. 

Operating mode 

mechanical, inductive 

Sensor element 

Pressure bellows or diaphragm 


G 1/2 external and G 1/4 internal. 

On FH types: G 1/4 internal. 

Cable entry 2 x M 16 x 1.5 

Degree of protection IP 65 

Installation 

Directly on the pressure line or mounted on wall with two 4 mm ø 

screws. 

Materials 

see Product Summary. 

Linearity 

The maximum linearity error is approx. 1% of full scale. 

Hysteresis 

approx. 0.5% nominal range, related to full output 

0–10 V or 0–20 mA. 

Long-term drift 

0.2% FS / year 

Repetition accuracy approx. 0.2% 

Accuracy class 1.0 

Temperature drift 

Range from 20–45°C approx. 0.02%/K 

Range from 0–20°C approx. 0.05%/K 

Influence of static pressure < = 3%/bar (see adjusting instructions, page 72) 


Vertical. With other mounting positions, the degree of protection 

and accuracy are different. 

Ambient temperature 0 to 45°C 

Max. medium temperature 70°C. Temperatures may reach 85°C for short periods. Higher 

medium temperatures are possible if the above limit values for the 

switching device are ensured by suitable measures (e.g.siphon). 

Storage temperature 

–20 to +70°C 


! Important: 

When connecting to control systems 

with a common AC supply, the ground 

conductor must be looped through. That 

is to say, on all devices in the system, 

the same reference potential must be 

present at the corresponding ground terminal 

(terminal 2). In the case of a DC 

supply, ensure correct polarity. 

ED 3 output signal 0–10 V


71 

Type series F 

Adjustment and operation 

Operating ranges and output signals are adjustable 

over a wide range. 

An outstanding characteristic of the pressure transmitters is the variability of the characteristic curve, 

which means that the pressure range and output signal can be adapted to any subsequent control 

system. 

P0 = starting pressure of nominal range 

PN = nominal pressure (end point of nominal range) 

PA = starting pressure of set range 

PE = end pressure of set range 

Operator interface ED 1 

1 = Setting spindle for setting 

the final value PE 

2 = Setting potentiometer for setting 

the initial value PA 

3 = Slide switch for selecting the 

output signal 0–20 mA (0–10 V) 

or 4–20 mA (2–10 V) 

4 = Slide switch for inverting the 

output signal 

5 = Slide switch for changing the 

steepness of the characteristic 

in a ratio of 8:5. 

Normal position: 8 

For smaller operating ranges 

(< approx. 70% of the nominal 

range), select position 5 

6 = Plug connector for further evaluation 

modules 

Output signals for module ED 1 

Basic setting 

The factory default setting covers the nominal range P0 

(usually 0 bar) to PN. 

Altering the range 

The range can easily be altered by shifting the end point and 

adjusting the steepness of the characteristic curve. 

Inversion 

The output signal can be inverted by means of a slideswitch. 

Operator interface ED 3 

1 = Setting spindle for setting 

the final value PE 

2 = Setting potentiometer for setting 

the initial value PA 

4 = Slide switch for inverting the 

output signal 

6 = Plug connector for further evaluation 

modules 

Output signals for module ED 3 

Range alteration and inversion as above. 

The current signal can be reduced below 4 mA (down to approx. 

2.5 mA). If the installation has a fault alarm system, the response 

threshold should be set below 2.5 mA.

72 


Type series F 

Setting and testing 

Altering the operating range 

To check functioning or change the settings from outside the system, a test set-up is required which 

meets the following requirements: 

1. It must be possible to apply pressure to the pressure transmitter up to the desired final value. The 

pressure must be displayed by a sufficiently accurate pressure gauge. 

2. To display the output signal a voltmeter with a measuring range of 0–10 V (preferably 0–15 V) or an 

ammeter with a measuring range of 0–20 mA (preferably 0–25 or 0–30 mA) are required. 

3. To supply power to the transmitter, a 24 V AC or 24 V DC voltage source is needed. 

Setting operations must be carried out in the correct sequence 

1. Remove the plastic cover 

2. Set the slide switches (3) and (4) to the correct position (switch 3 is only present on ED 1) 

Switch (3): Output signal 0–10 V / 0–20 mA or 4–20 mA / 2–10 V (only on ED 1) 

Switch (4): Direction of action 

Switch up 

rising pressure = rising output signal 

Switch down (INV): rising pressure = falling output signal 

3. Loosen the locking screw above the cover glass (approx. 2 turns anticlockwise) 

4. Apply final pressure PE 

5. Using a screwdriver, turn the setting spindle (1) to the desired output signal (depending on position 

of slide switches (3) and (4): 10 V, 20 mA, 0 V, 0 mA, 4 mA) 

6. Apply starting pressure PA 

With the potentiometer (2), adjust the output signal to the desired value (depending on position of 

slide switches: 0 V, 0 mA, 10 V, 20 mA, 4 mA) 

7. Check the setting again and then retighten the locking screw for the setting spindle. 

Important: Always set the upper final value PE with the setting spindle (1) first, and then the 

lower initial value PA with the potentiometer (2). 

Generating an output signal without pressure 

It can often be very useful to generate an output signal before commissioning the system, in order to 

check electrical operation, the direction of action and the functioning of downstream control elements. 

The procedure is as follows: 

1. Loosen the four screws on the scale window and remove the cover glass, scale plate 

and rubber seal. 

2. In the lower, wide part of the cut-out in the housing, insert the tip of a small screwdriver 

underneath the bridge. 

3. Carefully move the bridge up and down. When the supply voltage is applied, the output signal 

should change depending on the movements of the bridge. 

4. Check the direction of action. Upward movement of bridge corresponds to rising pressure. 

5. Once you have finished testing, carefully screw the parts back on again in the following order: 

rubber seal, scale plate, cover glass. 

Caution: In the event of incorrect assembly, IP 65 protection is no longer assured. 

Adjustment instructions: Correction of effect with static pressure 

· The system in which the FHBN is installed must be filled and exposed to the usual static pressure. 

· A differential pressure must not be active, i.e. no pump operation and no flow. 

· Remove the plastic cover and check slide switches 3 + 4. 

· The FHBN is supplied with the correct voltage and the output voltage is displayed. 

· Loosen the spindle locking screw above the inspection window. 

· Adjust setting spindle “1” with a screwdriver until the output signal is “0”. 

· Retighten the spindle with the spindle locking screw.



73 

Type series F 


1 

2 

3 

Dimensioned drawing no. Types 

A 

1 FN 025-FN 3 55.5 

FVN… 

2 FHBN… 90 

3 FN 505, FN 510 82 

Height of evaluation module = 1 Module height = 34 mm. 

The dimensions are for the basic device, consisting of sensor and 

evaluation module. 

Each further plug-in module increases the overall height by one 

module unit = 34 mm.

74 


for liquid and gaseous media 

Type series SN 3 

Pressure transmitters, piezoresistive, 3-conductor system 

Type series SN…311 

2 output signals 

0–10 V and 4–20 mA 

The nominal ranges of types SN…311 mentioned 

in the Product Summary below can be 

limited by 50% of the nominal range via setting 

potentiometers of the evaluation electronics. The 

smallest settable operating range is indicated in 

column 2 of the Product Summary. The zero 

point can likewise be shifted by 50% of the 

nominal range. 

Inversion of output signal possible on SN…-311 

and …-395. 



Pressure connection G 1/2 external, wrench 

size 27 

Cable entry 2 x Pg 9 


Mounting 

Directly on pressure 

line 

Materials 

Sensor housing: 

1.4571 

Pressure diaphragm: 

1.4435 

Terminal housing: 

Makrolon 

Service life 100m cycles (typical) 

Dimensions See page 73. 

Operating voltage 24 V AC ± 20% or 24 

V…36 V DC 

Power consumption max. 1 W 

Synchronization error max. ± 0.3% FS 

of voltage and 

current output 

on SN 311 

Load impedance 

0–10 V impedance 

> 10 kOhm 

4–20 mA impedance 

650 Ohm 

max. ± 0.5% FS 

max. ± 0.1% FS 

max. ± 0.5% FS 

Linearity error 

Hysteresis 

Temperature 

hysteresis 

Reproducibility max. ± 0.1% FS 

Overall accuracy 1% 

Medium temperature –30 to 100°C 

Compensated range 0–100°C 

Temperature drift max. ± 0.04% FS/K 

Ambient temperature 0–50°C 

Inversion of On SN…311 

output signal and SN 395 

LED digital display Powered via 

(optional) 

transmitter. 

AZ 331 

No separate supply 

needed. 

Operating range Smallest settable Max. permissible Type 

(nominal range) operating range pressure 

(bar) (bar) (bar) 

2 output signals 0–10 V and 4–20 mA terminal connection, range adjustable 

0 – 0.25 0.125 0.75 SN 025-311 

0 – 0.6 0.3 1.8 SN 06-311 

0 – 1 0.5 3 SN 1-311 

0 – 2.5 1.25 7.5 SN 3-311 

0 – 6 3 18 SN 6-311 

0 – 10 5 30 SN 10-311 

0 – 25 12.5 70 SN 25-311 

0 – 40 20 80 SN 40-311 

Output signal 0–10 V plug connection, range adjustable via jumpers (50%, 20%) 

0 – 0.25 0.05 0.75 SN 025-395 

0 – 0.6 0.12 1.8 SN 06-395 

0 – 1 0.2 3 SN 1-395 

0 – 2.5 0.5 7.5 SN 3-395 

0 – 6 1.2 18 SN 6-395 

0 – 10 2 30 SN 10-395 

0 – 25 5 70 SN 25-395 

0 – 40 8 80 SN 40-395 

Connection scheme SN…311 Connection scheme SN 395 

Type series SN…395 

Output signal 0–10 V 

Not adjustable, inversion not 

possible. Plug connection 

(digital display AZ 331) 

s 


IP 65


for liquid and gaseous media. 2-conductor system 

75 

Type series SN…-280 

The low-voltage plugs on SN transmitters 

can be opened up. This simplifies fitting 

and also means that the supply voltage and 

output signal can be measured directly from 

the opened plug. 

As-delivered condition: 

The transmitters are fully assembled in the 

factory (sensor + evaluation module + cover) 

and set to the nominal range. Additional 

modules and external modules are supplied 

separately. 

SN 280 


Electrical 


connection DIN 43650 PG 11 

Supply voltage 12 V…30 V DC 

Ambient temperature 0…+60°C 

Material 

Housing: Makrolon 

Sensor: 1.4571 

Diaphragm: 1.4435 


Included accessories Plug DIN 43650 

Pressure connection G 1/2 external 

Wrench size 27 

Installation Directly on 

pressure line 

Linearity 

1% FS 

Compensated range 0–100°C 

Response time 10 ms 

Max. medium –30…+110°C 

temperature 

Measuring principle Piezoresistive 

Mounting 

Directly on 

pressure line 

Output signal 4…20 mA, impedance 

(UB–10 V) / 0.02 A 

Overall accuracy 1% FS 

(fixed-point line) 

Ambient temperature 0…60°C 

Direction of action Rising pressure produces 

rising output 

signal 

Accessories Plug-in display 

AZG 241 


Operating range Operating range Max. pressure Type 

(bar) (kPa) (bar) 

0 – 0.25 0 – 25 0.75 SN 025-280 

0 – 0.6 0 – 60 1.8 SN 06-280 

0 – 1 0 – 100 3 SN 1-280 

0 – 1.6 0 – 160 6.4 SN 2-280 

0 – 2.5 0 – 250 7.5 SN 3-280 

0 – 4 0 – 400 16 SN 4-280 

0 – 6 0 – 600 18 SN 6-280 

0 – 10 0 – 1000 30 SN 10-280 

0 – 16 0 – 1600 48 SN 16-280 

0 – 25 0 – 2500 70 SN 25-280 

0 – 40 0 – 4000 80 SN 40-280 

Connection scheme SN…-280 

The power supply is connected to 

terminals 1+ / 2– 

s 


IP 65

76 



Operator interface / operating ranges 

3-conductor systems (SN…–3) 

Adjusting elements: 

1 = zero point 

2 = end point 

INV = direction of action (INVERSION) 

Optical indication of output signal via LED 

The LED becomes brighter as the output signal 

increases. A zero signal can be displayed by 

briefly operating the INV switch. With output signal 

“0” and the slide switch in the “INV” position, 

the LED is brightly lit. 

Do not forget to turn the switch back! 

Operator interface 

The adjusting elements are accessible 

after removing the cover glass 

on the evaluation module. 

Operating ranges are adjustable over a wide range 

Basic setting 

The factory default setting covers 

the nominal range P0 (usually 0 

bar) to PN. 

P0 = Starting pressure of nominal 

range 

PN = Nominal pressure (end 

point of nominal range) 

PA = Starting pressure of set 

range 

PE = End pressure of set range 

Altering the range 

The range can easily be altered 

by shifting the zero point and 

adjusting the steepness of the 

characteristic curve. 

Observe the correct sequence of 

adjustment (see next page). 

Inversion 

(only on 3-conductor system) 

The output signal can be inverted 

with the “INV” slide switch. 

Inversion not possible 

on 2-conductor system.

Pressure transmitters 77 


Setting the operating range, testing 

Preliminary remark: The transmitters are carefully set in the factory to the nominal range. If the operating 

range is changed to different values, the guaranteed accuracy no longer applies. 

The attainable accuracy depends, among other things, on the care taken during adjustment. 

Warm up the device before making adjustments. 

Accurate settings are only possible with the device at operating temperature; therefore connect the 

power supply approximately 10 minutes before starting to make adjustments. 

Setting operations must be carried out in the correct 

sequence 

1. Apply minimum pressure PA to the sensor and set the output signal to 0 V or 4 mA 

with potentiometer 1. 

2. Apply maximum pressure PE to the sensor. Set output signals to 10 V / 20 mA 

with potentiometer 2. 

3. Check the settings. 

Important: Always set the zero point with potentiometer 1 first, then set the amplification (end of 

range) with potentiometer 2. 

For inversion of the output signal, operate slide switch INV and repeat the setting procedure in the 

same way. Inversion is only possible on 3-conductor systems. 

The plug-in digital display AZ facilitates accurate setting 

Digital display AZ 331 (additional module) can be very useful for setting operating ranges which differ 

from the nominal range. The digital display (factory setting 0–10 V) plugs into the connector 6 and 

shows the output signal continuously during the setting process. 

Device arrangement for calibration and testing from outside 

the system 

To check functioning or change the settings from outside the system, a test set-up is required which 

meets the following requirements: 

1. It must be possible to apply pressure to the pressure transmitter up to the desired final value. The 

pressure must be displayed by a sufficiently accurate pressure gauge. 

2. To display the output signal a voltmeter with a measuring range of 0–10 (preferably 0–15 V) or an 

ammeter with a display range of 0–20 mA (preferably 0–25 or 0–30 mA) are required. 

3. To supply power to the transmitter, a 24 VAC or 24 VDC voltage source is needed.

78 



Type series SN 


SN…311 

SN…-395/-280 

Type series DPT (D) 


65.05 

50 

¯ 6 

57.5 

22 

7.5 

18 

59 

M1:1 

8.5 

¯ 4.5


for gaseous, non-aggressive media 

79 

Type series DPT (D) 

Differential pressure transmitters 

Applications 

· Air-conditioning and ventilation systems 

· Building automation 

· Environmental protection 

· Fan and ventilator control 

· Valve and shutter control 

· Filter and fan monitoring 

· Liquid and level monitoring 

· Controlling of air flows 

DPT 1000 D 


Pressure media Air, and non-combustible 

and non-aggressive 

gases. 

Pressure Plastic connection piece 

connection with 6 mm external 

diameter for measuring 

hose with 5 mm internal 

diameter. 

Connector P 1 for higher 

pressure, P 2 for lower 

pressure. 

Cable entry / M 20 x 1.5, screw termielectrical 

nals for wires and leads 

connection with conductor crosssection 

up to 1.5 mm 2 . 

Degree of protec- IP 54 with cover, 

tion according to IP 00 without cover 

DIN 40050 

Mounting Any mounting position 

possible, with screws 

supplied 

Materials Transmitter housing and 

pressure connection P2 

made of ABS, light grey. 

Fastening element with 

pressure connection P1 

made of POM, white. 

Long-term stability -50 Pa - 1000 Pa 2.5; 

in % FS/year 1000/2500 Pa 1.5 

Repetition accuracy < ± 0.2% of final value 

Linearity and < ± 1% of end value 

hysteresis factor 

Response time switchable 

100 ms/1sec 

Medium and am- –10°C to +70°C 

bient temperature 

Permitted air 0–95% non-condensing 

humidity (2-conductor DC only!) 

Operating voltage 18…30 V AC, 16–32 V 

DC (2-conductor DC 

only) 

Max. current 30 mA for AC, 20 mA 

consumption for DC 

Power consumption Max. 1 W 

Output signal 0–10 V, short-circuitproof 

to ground 

4–20 mA, short-circuitproof 

30 mA 

Housing dimensionsDiameter 

and weight 85 mm x 58 mm, 130 g 

Standards and EN 60770, EN 61326 

conformity 

Supplied 

accessories: 

Optional 

accessories: 

2 m silicone hose, 

2 connection pieces with 

fastening screws, 

2 self-tapping screws for 

fastening the housing 

DPSL L-shaped bracket 

for installation turned 

through 90°, e.g. in ceiling 

area 


Type Default Operating range Over- Bursting Temperature 

operating extended by pressure pressure error 

range in Pa jumpers in Pa in kPa in kPa 

Versions with output voltage 0 - 10 V 

DPT 50 -50 … + 50 not possible 20 40 ± 5% FS 

DPT 110 -100 … +100 not possible 20 40 ± 5% FS 


DPT 1100 -1000 …+1000 not possible 40 70 ± 1% FS 

DPT 100 0 - 100 0 - 250 20 40 ± 5% FS 

DPT 250 0 - 250 0 - 500 20 40 ± 5% FS 

DPT 500 0 - 500 0 - 1000 20 40 ± 2.5% FS 

DPT 1000 0 - 1000 0 - 2500 40 70 ± 1% FS 

Versions with output voltage 0 - 10 V and digital display 

DPT 50 D -50 ... +50 not possible 20 40 ± 5% FS 



DPT 1100 D -1000 ...+1000 not possible 40 70 ± 1% FS 

DPT 100 D 0 - 100 0 - 250 20 40 ± 5% FS 

DPT 250 D 0 - 250 0 - 500 20 40 ± 5% FS 

DPT 500 D 0 - 500 0 - 1000 20 40 ± 2.5% FS 

DPT 1000 D 0 - 1000 0 - 2500* 40 70 ± 1% FS 

Versions with current output 4 - 20 mA (3-conductor) 

DPT 53 -50 … + 50 not possible 20 40 ± 5% FS 


DPT 553 -500 ... +500 not possible 20 40 ± 1% FS 

DPT 1103 -1000 ... +1000 not possible 40 70 ± 1% FS 

DPT 103 0 - 100 0 - 250 20 40 ± 5% FS 

DPT 253 0 - 250 0 - 500 20 40 ± 5% FS 

DPT 503 0 - 500 0 - 1000 20 40 ± 2.5% FS 

DPT 1003 0 - 1000 0 - 2500 40 70 ± 1% FS 

Versions with current output 4 - 20 mA (3-conductor) and digital display 





DPT 103 D 0 - 100 0 - 250 20 40 ± 5% FS 

DPT 253 D 0 - 250 0 - 500 20 40 ± 5% FS 

DPT 503 D 0 - 500 0 - 1000 20 40 ± 2.5% FS 

DPT 1003 D 0 - 1000 0 - 2500* 40 70 ± 1% FS 

Versions with current output 4 - 20 mA (2-conductor) 

DPT52 -50 … + 50 not possible 20 40 ± 5% FS 

DPT112 -100 … +100 not possible 20 40 ± 5% FS 

DPT102 0 - 100 0 - 250 20 40 ± 5% FS 

DPT252 0 - 250 0 - 500 20 40 ± 5% FS 

DPT502 0 - 500 0 - 1000 20 40 ± 2.5% FS 

DPT1002 0 - 1000 0 - 2500 40 70 ± 1% FS 

*pressure displayed in kPa 

s 


IP 54/00

80 


Adjustable display range 

Type series AZ 

Digital display, plugs onto transmitter 

AZ 331 

AZ display modules show the output of a transmitter 

from the MODUFLEX system on an LED 

display. 

On 3-conductor systems the supply and signal 

voltage is led from the evaluation module via ribbon 

cable. No additional wiring is needed. 

The starting and end values of the display can 

be set anywhere between -50 and +1199, so 

that any display range can be assigned to any 

pressure range. The decimal point can be 

moved with a slide switch. 

The y-signals of the transmitter can thus be displayed 

in any unit, e.g. V, mA, bar, mbar, %,°C, 

°F, psi, m, cm (filling level), m 3 , cm 3 (volume) etc. 


Display 

3 1/2 digit LED display, 

7 mm high, adjustable 

display range: 

–50 to +1999 

Supply voltage 24 VAC or 24 VDC. 

Via ribbon cable from 

the basic module 

Signal voltage (input) 0–10 V. 

Signal input via ribbon 

cable from the evaluation 

module or from other 

modules. Signal input 

switchable with slide 

switch 9. 

Normal setting: D 

(output signal from evaluation 

module is displayed) 

Decimal point Set with slide switch 

Factory setting Input signal 0–10 V 

0–10.00 ± 1 digit 

Power consumption Max. 1 W 

Degree of IP 65, in the installed 

protection state 

Dimensions Height: 

1 module unit = 34 mm 

By setting the input selector switch 9 to position E, the unit can be made to display signals generated 

by other modules. Furthermore, in its condition on delivery (factory setting 0–10.0), the display module 

can be used for accurately setting the operating range of a transmitter. All controls are accessible from 

the front, after removing the window. After setting, reinsert the window and press it in evenly. 


Type Suitable for Display Display range 

AZ 331 3-conductor systems 3 1/2 digit –50…+1999 

Controls 

Potentiometer 7 For setting lower display value (e.g. for y-signal 0%) 

Potentiometer 8 For setting upper display value (e.g. for y-signal 100%) 

Input selector switch 9 Position D: Output signal of the evaluation module is displayed 

(normal setting) 

Position E: Signal of another module is displayed 

Decimal point switch 10 For setting the decimal point 

Decimal point switch 11 Decimal point on/off 

Operator interface 

AZ 331 (3 1/2 digit) 

See above for description of 

controls.


Signal separators 

81 

Type series GT 

Electrical isolation of analogue transmitter signals 

The analogue output signals of a transmitter can 

be electrically isolated from the evaluation device 

using a signal separator. In this way, interference 

affecting the transmitter signal can be suppressed 

and influences caused by ground loops 

prevented. 

A signal separator is absolutely essential for 

transmitters whose output signals have to be 

transmitted over long distances and for signal 

lines which are exposed to strong electromagnetic 

radiation. 

GT 4 


Supply voltage 24 V AC ± 20% 

or 24–36 V DC. 

Power consumption 1.7 W 

Inputs 

Voltage signals, 

e.g. 0–10 V, 2–10 V, 

0–1 V and all voltage 

ranges between 

0 and 10 V 

Input resistor Ri > 220 kOhm 

Outputs Voltage signals 1:1 

from input signal, 

max. output signal 

current ± 1 mA 

Transformation ratio 1:1 

Channels 

4 channels, 

usable in parallel 

Linearity 

0.1% FS 

Transmission error max. 0.1% FS 

Interference Interference suppressuppression 

sion N according to 

EN 50 081-1 and 

EN 50 082-1, 

class B 


Protection class II 

Ambient temperature 0–50°C 

Mounting 

On mounting rail 

NS 35/7.5 to 

DIN 46 277 

The 4-channel configuration and the limitation to voltage signals results in very good value for money. 

Signal separator GT 4 is designed for 4 input signals between 0 and 10 V (e.g. 0–10 V, 2–10 V, 0–5 V, 

0–1 V). The input signal is conveyed to the output terminals in a ratio of 1:1. The input and output are 

electrically isolated. 


Type Channels Transformation Operating range 

GT 4 4 1 : 1 between 0 and 10 V 

All 4 channels can be used in parallel and independently of one another; however, the input and output 

channels are not electrically isolated from one another. 

Current signals of 0–20 mA or 4–20 mA in the input circuit can likewise be processed if a 500 ohm 

resistor with the requisite tolerance is attached to the input terminals. A proportional voltage signal is 

present at the output. The accuracy achieved in the separation of current signals and conversion into 

voltage signals essentially depends on the accuracy of the 500 ohm resistor that is used. With a resistor 

value of 500 ± 0.1%, a transmission accuracy of 0.3% is achieved. 

Schematic diagram 

Connection scheme 

Dimensions

82 


Programmable digital display 

Type series AP 

with 1 or 2 limit value switches for PT100, PT1000 

and voltage and current signals 

AP ... 

Various routines for setting the following parameters 

are integrated into the microprocessor-controlled 

digital display: 

· Measuring range (start and end point) 

· Display range (start and end point) 

· Setting of decimal point 

· 2 limit values (relays) and their hysteresis 

· Relay dropout or pickup delay 

· Scanning of minimum and maximum 

measured value 

· Rounding up or down of last digit 

· Averaging 


Input signals Freely selectable by 

setting jumpers. 


Housing front 48 x 96 mm (DIN) 

Dimension display On APT: °C 

On APV: none 

Display 

3 1/2 digit, 

LED 12.5 mm, red, 

automatic “–” sign 

Display range See Product Summary 

Other ranges 

adjustable 

Decimal point Programmable 

Measuring rate 2.5 measurements/ 

second 

Keyboard lockable with jumper (prevents 

input of commands) 

Switching outputs 2 x NO/NC contacts 

programmable 

Switching capacity 2 x 230 V, 5 A AC 

of output relay 

Supply voltage 230 V, 50–60 Hz, 3 VA 

Degree of protection IP 60, DIN 40 050 

(front) 

Working temperature –10 to +50°C 

Connection method Lift terminals 

Front panel cut-out H x W: 44.5 x 90.5 mm 

Max. installation 115 mm 

depth 

All routines and parameters can be set with keys on the front. The switching status of the relays is displayed 

by LEDs. Setting is buffered. If the supply voltage is interrupted, the set parameters are 

retained. For powering transmitters, an electrically isolated 24 VDC power supply (max. 30 mA) is 

available. 


Type Input signals Display range Suitable Stages 

(programmable) (programmable) for 

APV 600 0–1 V DC –1999 Pressure and 1 switching point 

APV 630 0–10 V DC to temperature 2 switching points 

0–20 mA DC +1999 transmitters 

APT 600 Pt 100 / Pt 1000 –150°C to Temperature 1 switching point 

APT 650 +199.9°C sensors 2 switching points 

–200°C to Pt 100 / 

+800°C Pt 1000 

Dimensions



83 


Pressure switches/isolating amplifiers/ 

flow monitoring 

F + ED 1 

Pressure transmitter of modular design with 

terminal connection; operating range adjustable, 

supply voltage: 24 V AC/DC, nominal range …– 

… mbar/bar. Smallest range … mbar/bar 

Output signal (invertible): 0–10 V and 0–20 mA 

Output signal short-circuit and surge-proof up to 

24 V, with plug connector for further plug-in modules 

(e.g. digital display); type F…+ ED 1 

F + ED 3 


openable plug connection to DIN 43 650 

Operating range adjustable, supply voltage: 24 V 

AC/DC, nominal range …–… mbar/bar. Smallest 

range … mbar/bar Output signal (invertible): 

0–10 V, output signal short-circuit and surgeproof 

up to 24 V, with plug connector for further 

plug-in modules (e.g. digital display); 

type F…+ ED 3 

SN…311 


terminal connection; operating range adjustable 

via 2 potentiometers, supply voltage: 24 V 

AC/DC, nominal range …–… mbar/bar. Smallest 

range … mbar/bar Output signal (invertible): 

0–10 V and 0–20 mA, output signal short-circuit 

and surge-proof up to 24 V, with plug connector 

for further plug-in modules (e.g. digital display); 

type SN…-311 

SN…395 


openable plug connection to DIN 43 650, operating 

range adjustable via jumpers to 100%, 50%, 

20% of nominal range, supply voltage: 24 V 

AC/DC, range …–… mbar/bar Output signal: 

0–10 V, output signal short-circuit and surgeproof 

up to 24 V, with plug connector for further 

plug-in modules (e.g. digital display); 

type SN…-395 

PST… 

Electronic pressure switch/transmitter 

with 5-pole plug connection to DIN 

IEC 60947-5-2, supply voltage: 14…36 VDC 

Nominal pressure range …–… mbar/bar, 

output signal: 4–20 mA and 0–10 V, selectable 

and invertible 

DPT… 

Differential pressure transmitters for 

gaseous, non-aggressive media 

Output signal: 0–10 V, short-circuit-proof to 

ground, 4–20 mA, short-circuit-proof 30 mA, 

operating range…–…Pa; type DPT… 

AZ… 

Plug-in digital display (LED, 7 mm high), 

3 1/2 digit, supply voltage and signal voltage via 

basic module, display range adjustable; 

type AZ 331 

GT 4 

Signal separator, 4-channel, for standard railmounting, 

for electrical isolation of analogue transmitter 

signals between 0 V and 10 V, transformation 

ratio: 1:1, supply voltage: 

24 V AC/DC; type GT 4 

APV 630 

Programmable digital display with 2 limit 

value switches for panel surface mounting 

(standard dimensions 48 x 96 mm), 3 1/2 digit 

LED display, 12.5 mm, red, input signals: 

0–1 VDC, 0–10 VDC, 0–20 mA DC, 

programmable operating range and switching 

point, supply voltage: 230 V AC; type APV 630 

SN…280 


openable plug connection to DIN 43 650 Supply 

voltage: 11–36 V DC, range …–… mbar/bar, output 

signal: 4–20 mA (two-conductor) Output signal 

short-circuit and surge-proof up to 24 V; type 

SN…-280

Manufactured for and on behalf of the Environmental and Combustion Controls Division of Honeywell Technologies Sàrl, Ecublens, Route du Bois 37, Switzerland by its Authorized Representative: 

Fema Controls · Honeywell GmbH 

All technical data and illustrations are without obligation 

in relation to the supplied product. Subject to change. 

 

 

Printed in Germany · Identification number EN0B0562GE51 R05 06

Pressure

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